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A motorized filter slide for my DS287 on my Dob

 

My UC18 is getting a bit of automation.


Re: Which Digital Setting Circles to buy

 

Hi Olivier,
thank you for your answer. I will buy skyfi ?for sure, to use it with my mac wirelessly.
Clear skies, ¹ó°ù¨¦»å¨¦°ù¾±³¦


Re: Which Digital Setting Circles to buy

 

¿ªÔÆÌåÓý

Hello F¨¦d¨¦ric

?

I have a Classic 18¡± with AN/SC from the origin. I have connected the AN to SkySafari with SkyFi (wireless) and it works beautifully. Automatic tracking and Goto remains possible. I use SkySafari on my laptop to goto targets. So it¡¯s possible to do it without the need for replacing AN.

?

Olivier

?

Van: [email protected] <[email protected]> Namens ¹ó°ù¨¦»å¨¦°ù¾±³¦ Ruciak
Verzonden: zaterdag 7 augustus 2021 17:04
Aan: [email protected]
Onderwerp: Re: [ObsessionUsers] Which Digital Setting Circles to buy

?

Hi all,
I read the discussion and I have a question. I have a UC22 (real number one :-)) with AN/SC from the origin. I am interested by the nexus II / SkySafari use case. Is it compatible with SC ie will I keep GOTO and automatic tracking ?if I connect my encoders to nexus II and use sky safari to choose a target? Is it difficult to setup?
Thanks, ¹ó°ù¨¦»å¨¦°ù¾±³¦?




Dit e-mailbericht is gecontroleerd op virussen met Avast antivirussoftware.



Re: Which Digital Setting Circles to buy

 

Hi all,
I read the discussion and I have a question. I have a UC22 (real number one :-)) with AN/SC from the origin. I am interested by the nexus II / SkySafari use case. Is it compatible with SC ie will I keep GOTO and automatic tracking ?if I connect my encoders to nexus II and use sky safari to choose a target? Is it difficult to setup?
Thanks, ¹ó°ù¨¦»å¨¦°ù¾±³¦?


Re: Which Digital Setting Circles to buy

 

With either Nexus or AN you can use them alone and push to your target but also having a tracking system is well worth the expense. ?To lock on your target and not have to recenter it makes viewing much more enjoyable, especially when doing outreach and not needing to recenter between each viewer. ?Likewise you don¡¯t have to worry about loosing the target when someone moves the scope. ?I installed ServoCAT myself - anyone can do it. ?Gary has excellent instructions and is available when you have questions. ?I agree with everyone about SkySafari, especially at public outreach. ?

Mike B


Re: Which Digital Setting Circles to buy

 

¿ªÔÆÌåÓý

Astrodevices sells encoders, but I got mine from Gary at ServoCat ( Stellarcat). You dont need anything more than 10k encoders¡­heck even 4K will be fine. Astrosystems also sells them


On Aug 6, 2021, at 4:02 PM, bob414 <bob414@...> wrote:

I see the Nexus II on the Astrodevices site, but I do not see where to get the encoders and cables for the Obsession Scope.? Or a complete kit for the Obsession preferred. ?Or final cost to get everything working.
?
Bob
?
?
?
From:?[email protected]?<[email protected]>?On Behalf Of?Don Payne via?
Sent:?Friday, August 6, 2021 3:52 PM
To:?[email protected]
Subject:?Re: [ObsessionUsers] Which Digital Setting Circles to buy
?
Bob414 - if you have thoughts on using an IPAD/Tablet then go with the Nexus II instead of the Nexus DSC. ?With the Nexus DSC you'll be using the keypad on the DSC itself to do things like 2-star alignment and such. ?To connect it to an IPAD/Tablet you'd need a separate Wifi adapter/card so, in my opinion, you'd be better off just getting the Nexus II. ?This way you'll use Sky Safari for 2-star alignment.?



--
Mark Bungart
15" Obsession #643 / Swayze mirror
Grove City, Ohio


Re: Which Digital Setting Circles to buy

Paul Weiler
 

¿ªÔÆÌåÓý

Best bet for encoders is astrosystems
Good luck


On Aug 6, 2021, at 4:02 PM, bob414 <bob414@...> wrote:

?

I see the Nexus II on the Astrodevices site, but I do not see where to get the encoders and cables for the Obsession Scope.? Or a complete kit for the Obsession preferred. ?Or final cost to get everything working.

?

Bob

?

?

?

From: [email protected] <[email protected]> On Behalf Of Don Payne via groups.io
Sent: Friday, August 6, 2021 3:52 PM
To: [email protected]
Subject: Re: [ObsessionUsers] Which Digital Setting Circles to buy

?

Bob414 - if you have thoughts on using an IPAD/Tablet then go with the Nexus II instead of the Nexus DSC. ?With the Nexus DSC you'll be using the keypad on the DSC itself to do things like 2-star alignment and such. ?To connect it to an IPAD/Tablet you'd need a separate Wifi adapter/card so, in my opinion, you'd be better off just getting the Nexus II. ?This way you'll use Sky Safari for 2-star alignment.


Re: Which Digital Setting Circles to buy

Don Payne
 

Dave at Obsession sells an encoder kit along with the brackets for $450. ?I believe he could install it for you as well, but I'm sure you and your club members could DIY. ?


Re: Which Digital Setting Circles to buy

 

¿ªÔÆÌåÓý

I see the Nexus II on the Astrodevices site, but I do not see where to get the encoders and cables for the Obsession Scope.? Or a complete kit for the Obsession preferred. ?Or final cost to get everything working.

?

Bob

?

?

?

From: [email protected] <[email protected]> On Behalf Of Don Payne via groups.io
Sent: Friday, August 6, 2021 3:52 PM
To: [email protected]
Subject: Re: [ObsessionUsers] Which Digital Setting Circles to buy

?

Bob414 - if you have thoughts on using an IPAD/Tablet then go with the Nexus II instead of the Nexus DSC. ?With the Nexus DSC you'll be using the keypad on the DSC itself to do things like 2-star alignment and such. ?To connect it to an IPAD/Tablet you'd need a separate Wifi adapter/card so, in my opinion, you'd be better off just getting the Nexus II. ?This way you'll use Sky Safari for 2-star alignment.


Re: Which Digital Setting Circles to buy

Don Payne
 

Bob414 - if you have thoughts on using an IPAD/Tablet then go with the Nexus II instead of the Nexus DSC. ?With the Nexus DSC you'll be using the keypad on the DSC itself to do things like 2-star alignment and such. ?To connect it to an IPAD/Tablet you'd need a separate Wifi adapter/card so, in my opinion, you'd be better off just getting the Nexus II. ?This way you'll use Sky Safari for 2-star alignment.


Re: Which Digital Setting Circles to buy

 

The new Nexus DSC version has a discount right now:?


On Fri, Aug 6, 2021 at 8:50 AM Don Payne via <djops=[email protected]> wrote:
I agree with Mark B and Paul W - the Nexus II with Sky Safari is super easy to use and set up.? It really enhanced the observing experience with my 20" F/5, it even works if you already have encoders installed.? After years of using the StellarCat/ArgoNavis Goto system, I migrated to the Nexus because I didn't need the tracking functionality and you don't need goto when you can just move the scope by hand while watching its position on the Sky Safari app.


Re: Which Digital Setting Circles to buy

Don Payne
 

I agree with Mark B and Paul W - the Nexus II with Sky Safari is super easy to use and set up. ?It really enhanced the observing experience with my 20" F/5, it even works if you already have encoders installed. ?After years of using the StellarCat/ArgoNavis Goto system, I migrated to the Nexus because I didn't need the tracking functionality and you don't need goto when you can just move the scope by hand while watching its position on the Sky Safari app.


Re: Which Digital Setting Circles to buy

 

I whole heartedly recommend the Nexus II/ iPad/Sky Safari solution. Its such a game changer and makes observing incredibly efficient and enjoyable.

Mark
Obsession15 #643
Swayze mirror

On Aug 6, 2021, at 9:53 AM, Paul Weiler <dc9fxer@...> wrote:

Hi
I have an Astro devises Nexus 2 and SkySafari. With encoders from astrosystems.
It¡¯s a well built easy to use system
Good luck
Paul
On Aug 6, 2021, at 9:32 AM, Linton Guise <lguise@...> wrote:

?I have the Argo Navis system fitted which I like, although some find the dial menu system strange to begin with. I¡¯ve also just started to use a Nexus 2 which links wirelessly to my iPad running SkySafari. It uses the same encoders so you can just switch between the two. This is a great visual interface and also gets around the problem of having a stalk for the Argo etc. The nexus has its own rechargeable battery and can be positioned in the rocker base with Velcro.
Well worth looking into but I like SkySafari with public outreach groups.

All the best

Linton

L.J.Guise
Physics Dept.
Bedford School.
www.bedfordschool.org.uk/observatory

This message has been sent through the Bedford School email Server, and is intended for the addressee(s) only. If you have received this message in error, please contact the sender, or administrator@..., and delete the email. The views expressed are the views of the sender, and not necessarily the views of the School. The information in this message may be confidential and should not be read, copied, or otherwise distributed unless permission is given.

Bedford School is part of The Harpur Trust: a company limited by guarantee. Registered in England: Company No. 3475202. Registered Office: Pilgrim Centre, Brickhill Drive, Bedford, MK41 7PZ. Registered Charity No. 1066861







--
Mark Bungart
15" Obsession #643 / Swayze mirror


Re: Which Digital Setting Circles to buy

Paul Weiler
 

Hi
I have an Astro devises Nexus 2 and SkySafari. With encoders from astrosystems.
It¡¯s a well built easy to use system
Good luck
Paul

On Aug 6, 2021, at 9:32 AM, Linton Guise <lguise@...> wrote:

?I have the Argo Navis system fitted which I like, although some find the dial menu system strange to begin with. I¡¯ve also just started to use a Nexus 2 which links wirelessly to my iPad running SkySafari. It uses the same encoders so you can just switch between the two. This is a great visual interface and also gets around the problem of having a stalk for the Argo etc. The nexus has its own rechargeable battery and can be positioned in the rocker base with Velcro.
Well worth looking into but I like SkySafari with public outreach groups.

All the best

Linton

L.J.Guise
Physics Dept.
Bedford School.
www.bedfordschool.org.uk/observatory

This message has been sent through the Bedford School email Server, and is intended for the addressee(s) only. If you have received this message in error, please contact the sender, or administrator@..., and delete the email. The views expressed are the views of the sender, and not necessarily the views of the School. The information in this message may be confidential and should not be read, copied, or otherwise distributed unless permission is given.

Bedford School is part of The Harpur Trust: a company limited by guarantee. Registered in England: Company No. 3475202. Registered Office: Pilgrim Centre, Brickhill Drive, Bedford, MK41 7PZ. Registered Charity No. 1066861





Re: Which Digital Setting Circles to buy

 

I have the Argo Navis system fitted which I like, although some find the dial menu system strange to begin with. I¡¯ve also just started to use a Nexus 2 which links wirelessly to my iPad running SkySafari. It uses the same encoders so you can just switch between the two. This is a great visual interface and also gets around the problem of having a stalk for the Argo etc. The nexus has its own rechargeable battery and can be positioned in the rocker base with Velcro.
Well worth looking into but I like SkySafari with public outreach groups.

All the best

Linton

L.J.Guise
Physics Dept.
Bedford School.
www.bedfordschool.org.uk/observatory

This message has been sent through the Bedford School email Server, and is intended for the addressee(s) only. If you have received this message in error, please contact the sender, or administrator@..., and delete the email. The views expressed are the views of the sender, and not necessarily the views of the School. The information in this message may be confidential and should not be read, copied, or otherwise distributed unless permission is given.

Bedford School is part of The Harpur Trust: a company limited by guarantee. Registered in England: Company No. 3475202. Registered Office: Pilgrim Centre, Brickhill Drive, Bedford, MK41 7PZ. Registered Charity No. 1066861


Which Digital Setting Circles to buy

 

Our club was recently donated an Obsession 18" classic.? We are trying to decided which Digital Setting Circles system to acquire.? Does anybody have the pro¡¯s and con's of each system?? Are we missing a third contender?

?

Bob


Re: 18 Obsession UC

 

I had a 22¡± primary from a top US manufacturer with excellent test report etc. When I first set it up in my scope it showed very bad astigmatism, there had to be a problem. I tracked it down to the triangular mirror supports which were not spreading the load equally. Once I resolved this the glass settled into shape again and the views are stunning!
I know the 18¡±UC has issues holding collimation, I had one and sold it for that reason, but I would look at your mirror supporting structures.
Just a thought from, for once, a warm clear corner of England!

Linton

L.J.Guise
Physics Dept.
Bedford School.
www.bedfordschool.org.uk/observatory

This message has been sent through the Bedford School email Server, and is intended for the addressee(s) only. If you have received this message in error, please contact the sender, or administrator@..., and delete the email. The views expressed are the views of the sender, and not necessarily the views of the School. The information in this message may be confidential and should not be read, copied, or otherwise distributed unless permission is given.

Bedford School is part of The Harpur Trust: a company limited by guarantee. Registered in England: Company No. 3475202. Registered Office: Pilgrim Centre, Brickhill Drive, Bedford, MK41 7PZ. Registered Charity No. 1066861


Re: 18 Obsession UC

 

¿ªÔÆÌåÓý

In all fairness I must confess that if the UC-18 is assembled and left assembled it probably would have performed much better in the collimation holding department.? I used this scope for two years of heavy (sometimes more than two or three times a month) astronomy public outreach all over South Eastern Virginia. ?I became expert at setup and teardown.? I can set the scope up and collimate in just under 25 minutes, quicker if it isn¡¯t dark.? It has travelled to Green Bank WV, Coinjock NC, and hundreds of cub scout and school locations and now Colorado.? I can¡¯t understand the poor views with this mirror.? I was contemplating having New Moon Telescopes in Virginia to supply one of their Dobsonian carcasses and have the mirror recoated/refigured but the opportunity to buy a 20¡± Obsession Classic arose.

?

?

v/r

Chuck Jagow

Future ???????

Gone... ??????

?

?

From: <[email protected]> on behalf of Jeff Martin <jeff@...>
Reply-To: <[email protected]>
Date: Tuesday, July 20, 2021 at 9:12 AM
To: <[email protected]>
Subject: Re: [ObsessionUsers] 18 Obsession UC

?

I have an UC18.? It served me well when my home observations were on an upstairs deck.? Since I no longer have to climb stairs with a big dob and I won¡¯t be putting a big dob on a plane, I would now pick a classic style over the UC for a variety of reasons.? Far less tinkering and inter-part interference, etc.

?

I¡¯m surprised and curious about the mirror.? It¡¯s not like Terry is new to figuring or that his shop doesn¡¯t go through a number of interferometry tests with each mirror; seems like quality would be pretty well controlled.

?

The primary reason I¡¯m keeping my UC is because it holds a 17.5¡± coulter that he figured to .96 strehl for me (and that mirror has some family history).

?

-jeff

?

?

?

From: [email protected] [mailto:[email protected]] On Behalf Of charles jagow
Sent: Tuesday, July 20, 2021 7:21 AM
To: [email protected]
Subject: [ObsessionUsers] 18 Obsession UC

?

I bought my Obsession 18¡± UC several years ago after the owner had contracted a serious medical condition while he was waiting to receive the scope from Obsession.? He sold me the scope and had never even been able to look through it.? It was essentially brand new.? I previously owned briefly another brand of ¡°compact¡± Dobsonian with a 20¡± mirror.? The optics were excellent on the 20¡± but the packaging (mount) was worse than a dime store refractor¡¯s tripod.? That is another very long story, but suffice it to say I returned the 20¡± and about a week later acquired the 18¡± UC.

?

At this point in my Dobsonian stable I have the new to me 20¡± Obsession Classic, an 18¡± Obsession UC, an Orion 12¡± truss tube goto (which I believe, and many others have conceded to as well, that it has the best 12¡± mirror they have ever looked through), a 10¡± Orion Intelliscope, and a fun little 6¡± Dob.? I have observed with many different dobs at many star parties, one of my observing buddies includes a very accomplished ATM fellow who has recently won the highest ATM award for Newtonian (Dob style) reflectors at Stellafane ¨C something he has accomplished more than once.? I have learned from some very seasoned and experienced observers, and I have looked through some amazing scopes and some not so amazing scopes.? And I will stand by my statement that my Obsession 18¡± UC Ostahowski mirror is not even very good, I dare say that my 10¡± Intelliscope has a better view.? The dismal performance of the UC¡¯s optics coupled with its inability of the UC design to remain collimated through a heavy night of observing and/or public outreach led me down the path to a Classic Obsession.? I tried to buy a NEW one from Dave, but they have abandoned the 20¡± Classic design in favor of the UC design.

?

?

v/r

Chuck Jagow

Future ???????

Gone... ??????

?

?

From: <[email protected]> on behalf of Jeff Martin <jeff@...>
Reply-To: <[email protected]>
Date: Tuesday, July 20, 2021 at 7:30 AM
To: <[email protected]>
Subject: Re: [ObsessionUsers] HELP! 20" Obsession Classic F5

?

The only way your Ostahowski mirror is exponentially worse is if you have it mounted upside down.

?

The diagonal is flat, so there isn¡¯t a multiplying/fudging factor.? As you move a secondary closer to a primary the light cone it intercepts gets bigger.? That¡¯s why you have ¡°planet killer¡± Newtonians:? with really slow focal ratios you can mount a small secondary and get better contrast.? ?¡± won¡¯t move you to another secondary size.

?

If it were me, I¡¯d cut ?¡± off, try the eyepieces and paracorr.? Then I¡¯d make another round cutting, if necessary.? Only because I¡¯ve overcut more than once.?

?

-jeff

?

?

From: [email protected] [mailto:[email protected]] On Behalf Of charles jagow
Sent: Tuesday, July 20, 2021 6:20 AM
To: [email protected]
Subject: Re: [ObsessionUsers] HELP! 20" Obsession Classic F5

?

Thank you for your help.? The previous owner contacted me after I had put the scope to bed last night.? He had the same problem, but he said he moved the mirror up via the collimation bolts such that his eyepieces (ETHOS) would come to focus.? I moved the mirror up with the collimation bolts to the point I could only see three threads of travel left on each.? I then re-collimated first with the Howie Glatter and then dialed it in with a visual Cat's Eye tool set.? This allowed my Nagler 17mm to pass through focus, allowing me to focus that eyepiece.? The seeing and transparency was horrible last night, but the view of Jupiter was very well defined with the Nagler 17.? Stars are well formed, a little comet shaped much closer to the edge.? The mirror combination is exponentially better than the Ostahowski mirror in my UC 18.

I was able to bring a few of the other eyepieces to focus, mostly those above 17mm.? The range of 7-12mm were not able to pass through focus inward, some were close but no banana. ? NONE of the eyepieces would come to focus with my adjustable Paracor.

My favorite eyepieces, Pentax XW series (5mm, 7mm,10mm, and 14mm) will not come to focus at all.

This issue must be corrected.? It is apparent to me that the strut poles are too long.? All of the poles measure the same length plus or minus a 1/32".? The depth of my blocks measures? 2 3/4" each, +/- 1/8".

I am inclined to cut my poles by a half of an inch each.? My non-existent? ATM skills/experience would tell me that this should solve my inward focus issue if I place the mirror in about the middle of the collimation bolt's travel.? What I don't know is what effect the Secondary mirror has on focal length calculations, if any at all.?

I am inclined to believe that either the 45 degree angle and/or just the reflection off of the secondary mirror has an effect on the focal length somehow???

Lets say I get my 17mm Nagler to come to focus with the mirror positioned (and collimated) near the midpoint of travel of the collimation bolts, if I then were to reduce the length of the poles by a 1/2", will this result in an extra 1/2" of inward focus travel at the focuser?? Or is this somehow increased or decreased due to the effect of the Secondary mirror??

v/r
Chuck J.


Re: 18 Obsession UC

Jeff Martin
 

¿ªÔÆÌåÓý

I have an UC18.? It served me well when my home observations were on an upstairs deck.? Since I no longer have to climb stairs with a big dob and I won¡¯t be putting a big dob on a plane, I would now pick a classic style over the UC for a variety of reasons.? Far less tinkering and inter-part interference, etc.

?

I¡¯m surprised and curious about the mirror.? It¡¯s not like Terry is new to figuring or that his shop doesn¡¯t go through a number of interferometry tests with each mirror; seems like quality would be pretty well controlled.

?

The primary reason I¡¯m keeping my UC is because it holds a 17.5¡± coulter that he figured to .96 strehl for me (and that mirror has some family history).

?

-jeff

?

?

?

From: [email protected] [mailto:[email protected]] On Behalf Of charles jagow
Sent: Tuesday, July 20, 2021 7:21 AM
To: [email protected]
Subject: [ObsessionUsers] 18 Obsession UC

?

I bought my Obsession 18¡± UC several years ago after the owner had contracted a serious medical condition while he was waiting to receive the scope from Obsession.? He sold me the scope and had never even been able to look through it.? It was essentially brand new.? I previously owned briefly another brand of ¡°compact¡± Dobsonian with a 20¡± mirror.? The optics were excellent on the 20¡± but the packaging (mount) was worse than a dime store refractor¡¯s tripod.? That is another very long story, but suffice it to say I returned the 20¡± and about a week later acquired the 18¡± UC.

?

At this point in my Dobsonian stable I have the new to me 20¡± Obsession Classic, an 18¡± Obsession UC, an Orion 12¡± truss tube goto (which I believe, and many others have conceded to as well, that it has the best 12¡± mirror they have ever looked through), a 10¡± Orion Intelliscope, and a fun little 6¡± Dob.? I have observed with many different dobs at many star parties, one of my observing buddies includes a very accomplished ATM fellow who has recently won the highest ATM award for Newtonian (Dob style) reflectors at Stellafane ¨C something he has accomplished more than once.? I have learned from some very seasoned and experienced observers, and I have looked through some amazing scopes and some not so amazing scopes.? And I will stand by my statement that my Obsession 18¡± UC Ostahowski mirror is not even very good, I dare say that my 10¡± Intelliscope has a better view.? The dismal performance of the UC¡¯s optics coupled with its inability of the UC design to remain collimated through a heavy night of observing and/or public outreach led me down the path to a Classic Obsession.? I tried to buy a NEW one from Dave, but they have abandoned the 20¡± Classic design in favor of the UC design.

?

?

v/r

Chuck Jagow

Future ???????

Gone... ??????

?

?

From: <[email protected]> on behalf of Jeff Martin <jeff@...>
Reply-To: <[email protected]>
Date: Tuesday, July 20, 2021 at 7:30 AM
To: <[email protected]>
Subject: Re: [ObsessionUsers] HELP! 20" Obsession Classic F5

?

The only way your Ostahowski mirror is exponentially worse is if you have it mounted upside down.

?

The diagonal is flat, so there isn¡¯t a multiplying/fudging factor.? As you move a secondary closer to a primary the light cone it intercepts gets bigger.? That¡¯s why you have ¡°planet killer¡± Newtonians:? with really slow focal ratios you can mount a small secondary and get better contrast.? ?¡± won¡¯t move you to another secondary size.

?

If it were me, I¡¯d cut ?¡± off, try the eyepieces and paracorr.? Then I¡¯d make another round cutting, if necessary.? Only because I¡¯ve overcut more than once.?

?

-jeff

?

?

From: [email protected] [mailto:[email protected]] On Behalf Of charles jagow
Sent: Tuesday, July 20, 2021 6:20 AM
To: [email protected]
Subject: Re: [ObsessionUsers] HELP! 20" Obsession Classic F5

?

Thank you for your help.? The previous owner contacted me after I had put the scope to bed last night.? He had the same problem, but he said he moved the mirror up via the collimation bolts such that his eyepieces (ETHOS) would come to focus.? I moved the mirror up with the collimation bolts to the point I could only see three threads of travel left on each.? I then re-collimated first with the Howie Glatter and then dialed it in with a visual Cat's Eye tool set.? This allowed my Nagler 17mm to pass through focus, allowing me to focus that eyepiece.? The seeing and transparency was horrible last night, but the view of Jupiter was very well defined with the Nagler 17.? Stars are well formed, a little comet shaped much closer to the edge.? The mirror combination is exponentially better than the Ostahowski mirror in my UC 18.

I was able to bring a few of the other eyepieces to focus, mostly those above 17mm.? The range of 7-12mm were not able to pass through focus inward, some were close but no banana. ? NONE of the eyepieces would come to focus with my adjustable Paracor.

My favorite eyepieces, Pentax XW series (5mm, 7mm,10mm, and 14mm) will not come to focus at all.

This issue must be corrected.? It is apparent to me that the strut poles are too long.? All of the poles measure the same length plus or minus a 1/32".? The depth of my blocks measures? 2 3/4" each, +/- 1/8".

I am inclined to cut my poles by a half of an inch each.? My non-existent? ATM skills/experience would tell me that this should solve my inward focus issue if I place the mirror in about the middle of the collimation bolt's travel.? What I don't know is what effect the Secondary mirror has on focal length calculations, if any at all.?

I am inclined to believe that either the 45 degree angle and/or just the reflection off of the secondary mirror has an effect on the focal length somehow???

Lets say I get my 17mm Nagler to come to focus with the mirror positioned (and collimated) near the midpoint of travel of the collimation bolts, if I then were to reduce the length of the poles by a 1/2", will this result in an extra 1/2" of inward focus travel at the focuser?? Or is this somehow increased or decreased due to the effect of the Secondary mirror??

v/r
Chuck J.


Re: 18 Obsession UC

 

Hi Chuck,
sorry to hear about your deception about your UC18.
I own a classic 15 and the very first UC22. This late one is special because I asked Dave to deliver side bearings in a single piece and I enlarged the secondary mirror to be sure not to loose a photon from the primary at large angular views. I would say that 1: you're right about the weakness of the 18UC 6 truss poles design to hold collimation on a wire range of altitude. This comes from the flexion of the single ring UTA and the fact that the focuser sits somewhere where it is not supported (not the case for UC22 with 8 truss tubes design), 2: I am very estonished to ear about a poor mirror coming from Obsession. My mirrors come from Obsession/OMI. What I know about the images they produce comes from several participations to the "rencontres astronomiques du printemps" in France where 200+ amateurs are gathering at 1100m altitude in a small city that shut down public lights for 3 nights in Craponne sur Arzon (it sounds french and it's right). All the expert fellows who looked through came back again and again to enjoy the night sky hopping with my UC22. Each time I am amazed both with planetary views (Jupiter wow and Saturn) as well as the galaxies and the veil and the globulars etc etc, contrast, sharpness. I do not know if you had the chance to star test your mirror with harold suiter's method described in the book titled star testing astronomical telescopes to detect any obvious default. I assume that you have a good collimation when you start observing. After that if you had been the first owner I know Dave would have exchanged the mirror but it's not your case.
¹ó°ù¨¦»å¨¦°ù¾±³¦