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I just acquired a 2007 classic Obsession 20" F5.? The scope looks to be in excellent shape.? I assembled the scope being careful to place the strut poles in the blocks according to the previous owners labels on the blocks and poles.? Attached the Upper Cage Assembly and collimated the mirrors with my HG laser and then also eyeballed it with the cats eye tools.? I just rolled the scope out to look at the moon.? I am unable to bring??? ANY?? of my eyepieces to focus on the moon.? 17mm Nagler, 35mm Orion Deep View, 42mm Deep view, 40 mm Meade Plossl, and many others, tried everything in my case.?
The focuser is racked all the way in, not enough inward travel.
I double checked to ensure the poles are fully seated in the blocks on the mirror box, and that the Upper Cage Assembly is properly seated on the poles and secured.
I have an Obsession 18 UC, but this is my first experience with an Obsession Classic.
What am I doing wrong??
I have had many DOBs but this is my first really big classic style.
v/r
Chuck J.
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I've got an 18" classic - you have quite a bit of up-travel on your mirror - run the collimation bots up a bit and see if that give you enough in travel. Just a thought.
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I would send this email to Dave Kriege.
On Mon, Jul 19, 2021 at 9:36 PM charles jagow < chuck@...> wrote: I just acquired a 2007 classic Obsession 20" F5.? The scope looks to be in excellent shape.? I assembled the scope being careful to place the strut poles in the blocks according to the previous owners labels on the blocks and poles.? Attached the Upper Cage Assembly and collimated the mirrors with my HG laser and then also eyeballed it with the cats eye tools.? I just rolled the scope out to look at the moon.? I am unable to bring??? ANY?? of my eyepieces to focus on the moon.? 17mm Nagler, 35mm Orion Deep View, 42mm Deep view, 40 mm Meade Plossl, and many others, tried everything in my case.?
The focuser is racked all the way in, not enough inward travel.
I double checked to ensure the poles are fully seated in the blocks on the mirror box, and that the Upper Cage Assembly is properly seated on the poles and secured.
I have an Obsession 18 UC, but this is my first experience with an Obsession Classic.
What am I doing wrong??
I have had many DOBs but this is my first really big classic style.
v/r
Chuck J.
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Read before send. BOLTS, not BOTS.
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I had a similar experience once but I found my collimation screws had backed out nearly all the way from extensive travelling/bumpy roads.
FYI, the truss poles on my 20" F5 classic are ~65-7/8" with ~2-3/4" inserted into the wood retaining blocks.
Hope this helps.
On Mon., Jul. 19, 2021, 8:36 p.m. charles jagow, < chuck@...> wrote: I just acquired a 2007 classic Obsession 20" F5.? The scope looks to be in excellent shape.? I assembled the scope being careful to place the strut poles in the blocks according to the previous owners labels on the blocks and poles.? Attached the Upper Cage Assembly and collimated the mirrors with my HG laser and then also eyeballed it with the cats eye tools.? I just rolled the scope out to look at the moon.? I am unable to bring??? ANY?? of my eyepieces to focus on the moon.? 17mm Nagler, 35mm Orion Deep View, 42mm Deep view, 40 mm Meade Plossl, and many others, tried everything in my case.?
The focuser is racked all the way in, not enough inward travel.
I double checked to ensure the poles are fully seated in the blocks on the mirror box, and that the Upper Cage Assembly is properly seated on the poles and secured.
I have an Obsession 18 UC, but this is my first experience with an Obsession Classic.
What am I doing wrong??
I have had many DOBs but this is my first really big classic style.
v/r
Chuck J.
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Greetings from someone from your old stomping grounds.? ? I agree with Mark, back off all the collimation screws/bolts, this positions the primary mirror the farthest from the secondary mirror and re collimate.? I had the same problem on my 12” Orion and recently on a 18” Obsession.? The 12” had a damaged threads on one bolt, I cleaned that up and was able to get the primary further back in the cell. ? You might have a situation where someone modified, the poles.? If you know anyone with the same scope, measure the pole length. ? Hope this helps. ? Bob (bill) Beuerlein ? ? ?
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From: [email protected] < [email protected]> On Behalf Of Mark Gregory Sent: Monday, July 19, 2021 10:38 PM To: [email protected]Subject: Re: [ObsessionUsers] HELP! 20" Obsession Classic F5 ? I've got an 18" classic - you have quite a bit of up-travel on your mirror - run the collimation bots up a bit and see if that give you enough in travel. Just a thought.
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I thought it sounds like he needs to get the primary mirror closer to the secondary...
On Mon., Jul. 19, 2021, 9:21 p.m. bob414, < bob414@...> wrote: Greetings from someone from your old stomping grounds.? ? I agree with Mark, back off all the collimation screws/bolts, this positions the primary mirror the farthest from the secondary mirror and re collimate.? I had the same problem on my 12” Orion and recently on a 18” Obsession.? The 12” had a damaged threads on one bolt, I cleaned that up and was able to get the primary further back in the cell. ? You might have a situation where someone modified, the poles.? If you know anyone with the same scope, measure the pole length. ? Hope this helps. ? Bob (bill) Beuerlein ? ? ? ? I've got an 18" classic - you have quite a bit of up-travel on your mirror - run the collimation bots up a bit and see if that give you enough in travel. Just a thought.
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Yes, he needs to move the primary up, closer to the secondary. I'll bet the collimation bolts are backed way out. Move that mirror up half an inch and see how that works.
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Hi Charles,
I agree with the previous answers, depending of the direction where you see you come close to focus, inward or outward, but you do not reach it, you have to move the mirror up if inward, down if outward to bring the focus point within the range of the focuser. It happens when collimation after collimation you move the mirror in the same direction up to a point where the focus point get out of the focuser range. Of course you will have to decollimate the primary.
贵谤é诲é谤颈肠
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I have had the same problem and it was because the mirror was not seated correctly. I agree with the above comments and would start with adjusting the mirror mount first.?
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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.
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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 ? ?
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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.
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Chuck, I have the same scope as you, Obsession 20” F/5, except that my focal ratio is actually 4.92 and my scope and mirror were made in 1999.? I have had them since new.? ? Your focal length is another factor in the pole length required.? What is your mirror focal ratio?? It should be marked on the rear of the mirror, or maybe on the edge.? I’ll check mine here and let you know the length of my poles.? You can compare.? By the way, I have Naglers from 5mm up through a 35mm Panoptic.? I also have an Explorer Scientific 14mm 100 degree EP.? All come to focus. ? Double check proper seating of the poles inside your blocks and proper seating of the poles inside the aluminum clamps at the top. I also concur with the others’ remarks about the collimation screws position, but you have adjusted that already. Has something gone awry in the mirror cell supports?? Perhaps occurring during vehicle transit.? ? If you do go through with cutting your poles, I recommend a large tubing cutter, available a Lowes and Home Depot. However, before I would cut them, I would try to understand what has changed since 2007 to require them to be cut. ?Presumably prior owners had no major issues, but maybe they had different eyepieces.? Measure twice, cut once, of course, but first know “the rest of the story”. ? Good luck. ? Charlie ?
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From: [email protected] < [email protected]> On Behalf Of charles jagow Sent: Tuesday, July 20, 2021 9:20 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.
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Mr. Starks, ? I contacted the previous owner, and he too had the same issue with focus, he adjusted the Primary “up” in the collimation bolts such that his bevy of ETHOS eyepieces would come to focus and never did anything more with it. ? I don’t own any ETHOS, I had a 10mm once but sold it as I didn’t care for it – probably the only person in the world to not care for the ETHOS line.? My favorite eyepieces are my Pentax XW collection, and sadly none of them will come to focus even with the mirror raised as high as I could get it.? ? I am going to remove the Primary and CLEAN it, it is filthy, I could barely see the center donut while collimating.? I will check the sling and try to ascertain if the mirror cell looks OK.? ? I believe the 20” F5 is a 2007 or 2008 production unit. ?
Future ??????? Gone... ?????? ? ? Chuck, I have the same scope as you, Obsession 20” F/5, except that my focal ratio is actually 4.92 and my scope and mirror were made in 1999.? I have had them since new.? ? Your focal length is another factor in the pole length required.? What is your mirror focal ratio?? It should be marked on the rear of the mirror, or maybe on the edge.? I’ll check mine here and let you know the length of my poles.? You can compare.? By the way, I have Naglers from 5mm up through a 35mm Panoptic.? I also have an Explorer Scientific 14mm 100 degree EP.? All come to focus. ? Double check proper seating of the poles inside your blocks and proper seating of the poles inside the aluminum clamps at the top. I also concur with the others’ remarks about the collimation screws position, but you have adjusted that already. Has something gone awry in the mirror cell supports?? Perhaps occurring during vehicle transit.? ? If you do go through with cutting your poles, I recommend a large tubing cutter, available a Lowes and Home Depot. However, before I would cut them, I would try to understand what has changed since 2007 to require them to be cut. ?Presumably prior owners had no major issues, but maybe they had different eyepieces.? Measure twice, cut once, of course, but first know “the rest of the story”. ? Good luck. ? Charlie ?
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From: [email protected] < [email protected]> On Behalf Of charles jagow Sent: Tuesday, July 20, 2021 9:20 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.
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charles jagow
Christine Zeltner
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