| mike bacanin |
| (professor emeritus) |
| 07/03/09 06:08 PM |
merging issues .
|
I have just re-acquired a pair of 12mm pentax orthos.
i have a denk std with SCD holders in Tak 128.
i've just viewed the moon and whereas i normally have no problem merging the images, i seemed to have a little trouble.
does anyone use .965 inch eyepieces? normally these ep's are not a perfect fit in their 1.25 adapters and get slightly offset when the adapter locking screw is tightened.
am i right this can decenter the eyepieces in the binoviewer and cause merging issues?
also i just tried a pair of 6mm 1.25 inch orthos and just cannot merge at x260
are these too small in fl?
mike
| Covey32 |
| (scholastic sledgehammer) |
| 07/03/09 06:54 PM |
|
Re: merging issues .
|
For many people, merging issues begin at around 10mm and below. In my case I get better results overall (and no merging problems) by keeping my shortest focal length eyepieces to 10mm and using a barlow or corrector ahead of the binoviewer in the optical train.
| mike bacanin |
| (professor emeritus) |
| 07/03/09 09:00 PM |
|
Re: merging issues .
|
i have an ocs on the diagonal giving focal lengths of 1456mm and 2600mm with powerswitch, so yes i agree that 10mm or longer is good.
anyone comment on the .965 issue?
mike
| suburbanskies |
| (sage) |
| 07/03/09 09:49 PM |
|
Re: merging issues .
|
Regarding the 0.965" to 1 1/4" adapter issue, your reasoning seems to make sense, Mike.
Frankly even with 1 1/4" eps in a Baader V binoviewer, I have to rotate the eps in order to get a good merge. A good merge always seems to require some fiddling, at least in my experience. Try backing off on the set screw and rotating. Hopefully you can find the sweet spot...
I like the idea of 12mm Pentax SMC orthos binoviewed. One day I hope to try a pair of 18mm Pentax orthos myself!
Mark
| mike bacanin |
| (professor emeritus) |
| 07/04/09 03:30 AM |
|
Re: merging issues .
|
Hi Mark,
what i have done is use an even paper shim to try to centre the eyepieces in the adapter, that should centre them fairly well.
there is a noticeable offset if you simply put the eyepiece in without any packing and just tighten the adapter setscrew.
i suppose ideally a custom machined adapter with friction fit for the eyepiece would ensure perfect centring.
mike
| walt99 |
| (member) |
| 07/04/09 07:43 AM |
|
Re: merging issues .
|
Hi Mike,
If you ask him, Russ will send you a pdf with simple instructions for collimating the SCD's.
I found that a little tweaking with the object in view works best.
You can email him through the Denk website, But I will PM his email address.
Good seeing, Walt
| suburbanskies |
| (sage) |
| 07/04/09 09:16 AM |
|
Re: merging issues .
|
Mike, if you can see a noticeable offset I think you can be quite sure that that's your problem. It'd be great if your paper idea works. If it does not and you are willing to spend some money, try obtaining Takahashi 0.965" collet holders and having a machinist attach it to a 1.25" sleeve. I've seen it done and looks great (and presumably works well), but pricey like your custom adapter idea.
Now that I think of it, finding a good 0.965"/1.25" adapter is one of the reasons why I've held off on finding a pair of 18mm SMCs!
Mark
| mike bacanin |
| (professor emeritus) |
| 07/04/09 03:24 PM |
| Attachment |
|
Re: merging issues .
|
I just redid the adapter shimming by using pro grade masking tape.
i applied a single even layer around the inside of the adapters,resuling in a perfect friction fit for the pentax's.
i noticed last night that the adapter setscrews fouled on the denk ep holders, so i've retapped the setscrew holes for 4mm metric stainless hex head grub screws, here's the result.
mike
| suburbanskies |
| (sage) |
| 07/04/09 03:40 PM |
|
Re: merging issues .
|
Looks very nice and tidy. Always great to find a simple, inexpensive solution! Let us know how your first light goes...
Mark
| mike bacanin |
| (professor emeritus) |
| 07/04/09 03:52 PM |
|
Re: merging issues .
|
Hi Mark
just did a daylight test on some very distant trees, detail was very impressive. hope the night performance is good!
Mike
| suburbanskies |
| (sage) |
| 07/04/09 04:27 PM |
|
Re: merging issues .
|
I bet it'll be just as good at night. Problem solved
| mike bacanin |
| (professor emeritus) |
| 07/04/09 04:59 PM |
|
Re: merging issues .
|
Thanks Mark! I'll post an update when we get a clear night.
ps, i have a pair of 16mm zeiss jenas on the way, should be really nice to bino,
Mike
| roadi |
| (professor emeritus) |
| 07/05/09 05:21 AM |
|
Re: merging issues .
|
Quote:
Mike, if you can see a noticeable offset I think you can be quite sure that that's your problem. It'd be great if your paper idea works. If it does not and you are willing to spend some money, try obtaining Takahashi 0.965" collet holders and having a machinist attach it to a 1.25" sleeve. I've seen it done and looks great (and presumably works well), but pricey like your custom adapter idea.
Now that I think of it, finding a good 0.965"/1.25" adapter is one of the reasons why I've held off on finding a pair of 18mm SMCs!
Mark
Second that!
I have a Baader/Celestron unit with 60 degr bent and with the units original EP collets I never manage to get the pictures merged when EP much under 32mm used. Until I modified it with a pair of Takahashi collets! The problem is solved but stil some litle problems with 8mm and under but as Mark says loosen the clamps and a litle fidling will do it
In short.. I believe the slightest off centering or tilt of the EP will become evident when short focus EP are used, 9mm > - and the shorter the F-ratio of the scope the worse it'l be IME.
When using 24.5 mm EP you'll have slop two times.. between the EP itself and the adapter and between the adapter and collet wich isn't favourable!
| suburbanskies |
| (sage) |
| 07/05/09 09:22 AM |
|
Re: merging issues .
|
Quote:
ps, i have a pair of 16mm zeiss jenas on the way, should be really nice to bino,
Mike
12mm Pentax and 16mm Jena orthos...a sweet line up, indeed!
| mike bacanin |
| (professor emeritus) |
| 07/05/09 02:00 PM |
|
Re: merging issues .
|
I just received the collimating instructions from Russ for the SCD's.
A critical check has just shown that one eyepiece was producing a tiny degree of horizontal error in the right side. this pretty much vanished with a slight rotation of the eyepiece.
i actually think the difference was so small it may not be noticeable.
i suppose considering the potential issues with these .965 inch ep's in adapters, that's a good result.
I'll certainly try to make sure the 16mm zeiss pair are shimmed carefully,although i suspect the longer focal length should help.
Mike
| rogerandgarf |
| (sage) |
| 07/07/09 09:23 PM |
|
|
Re: merging issues .
|
Would either of these .965 adapters solve your problem?
http://www.alpineastro.com/eyepiece_adapters/eyepiece_adapters.htm#Reducers
http://www.agenaastro.com/0-965-Telescope-Adapter-s/201.htm
| mike bacanin |
| (professor emeritus) |
| 07/08/09 02:44 AM |
|
Re: merging issues .
|
Hi Roger,
thanks for the link.
i have sorted the problem with careful shimming and retapping for a hidden grub screw instead of the set screw.
the adapter in first link is very similar to what i have, you would still have the same problem of the eyepiece being a slack fit in the adapter.
Mike
| rogerandgarf |
| (sage) |
| 07/08/09 07:01 PM |
|
|
|
Re: merging issues .
|
Mike, I was left with the same impression despite the product description that accompanied the Baader adapter.
However, the adapter that Agena stocks (temporarily out) attracted my attention in that it has a brass compression fitting, the kind we are all used to seeing in the 2"/1.25" adapters. I would think that would hold more promise.
I am still at a loss sometimes to explain why a more precise adapter isn't readily available, especially given the $$ that many of the .965 oculars command.
Good luck in your efforts!
| mike bacanin |
| (professor emeritus) |
| 07/09/09 02:52 AM |
|
Re: merging issues .
|
Roger,
the answer i think, is a self centring collet type adapter similar to the 1.25 inch ep holder on my Tak 128.
however i've searched and cannot find a .965 inch version.
Mike
| crazyqban |
| (sage) |
| 07/10/09 03:42 AM |
|
|
Re: merging issues .
|
Mike, I use eye guards the are made by Orion on all of my bino eyepieces and I believe that they help out immensely. You might want to consider giving them a try. Another benefit is that they block out stray light...
Sergio
| mike bacanin |
| (professor emeritus) |
| 07/11/09 02:00 PM |
| Attachment |
|
Re: merging issues .
|
Hi Sergio,
thanks for the eyeguard tip!
well, i've decided to bite the bullet and go for the final pair of eyepieces i need, a pair of 10mm zeiss jenas.
i've already got a pair of adapters on the way, and i've convinced myself that a pair of zeiss would go nicely into them!
no more eyepieces for a long time after!!
here's a photo of the zeiss 16mm pair in the slightly modified adapters with grub screws.
Mike