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AT65EDQ and triangle stars

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#1 gapalp

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Posted 04 January 2012 - 03:15 PM

There have been some recent posts regarding "pinched optics" and the AT65EDQ:
link1
link2

The stars in my AT65EDQ images look awfully similar. I chalked it up to guiding but now that I re-reviewed these posts, I think I might have the same problem. Any thoughts? I am going to email the vendor about it too.

Image1
Image2
Image3
Image4

One of the suggestions is to "loosen the retaining ring slightly", which fixed a previous users problem. I am not sure what that means though.

#2 LLEEGE

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Posted 04 January 2012 - 03:46 PM

The incoming side of the optic has a retaining ring which holds the glass in the cell.
First, extend the dew shield and unscrew it from the sliding ring and set aside. Next, unscrew the outer ring from the lens cell. This is just a ring to protect the threads of the lens cell. Inside, you will see a second retainer ring which holds the optics in place. There are two slots on either side which of this ring which allow the use of a spanner. You should re able to unscrew this with just your finger nails in the slots. Loosen this retainer ring 1/2 turn and re tighten it until it just touches the outer optic. Revers operation to put back together.

#3 gapalp

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Posted 04 January 2012 - 04:05 PM

Astronomics says to do it at the focuser end:

"Remove the focuser, unscrew the blue or black ring which has the housing the tight element is in. There is a silver ring with 2 notches in it that you can use a spanner wrench to loosen. Loosen it and then tighten it slightly and everything should be fine."

So which end is it? Plus, where do I get a spanner wrench?

#4 LLEEGE

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Posted 04 January 2012 - 04:35 PM

I guess it depends on which element is pinched. As far as where to get a spanner, you can make one or pick one up from a hardware store. I doubt you will need one. I can loosen mine with my fingers. You need to be careful not to slip and scratch the optic with any tools. Finger/fingernail is best.

#5 mclewis1

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Posted 04 January 2012 - 04:35 PM

A "spanner" is a generic name for a wrench.

What you are looking for is a pin spanner or pin wrench. There are a number of commercial sources (specialty tool suppliers that will show up on an online search for "pin spanner") for these but you can also make your own from a piece of wood and two nails. You drive the nails in at the same distance as the diameter of the ring you want to move. You then file down the ends of the nails so that they are narrow and squared so that they fit snugly into the little slots on the ring you want to move. If you're careful you can often build a pin spanner that will be an effective tool (no slipping) and will last for years of use.

#6 kw6562

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Posted 04 January 2012 - 05:57 PM

Astronomics says to do it at the focuser end:

"Remove the focuser, unscrew the blue or black ring which has the housing the tight element is in. There is a silver ring with 2 notches in it that you can use a spanner wrench to loosen. Loosen it and then tighten it slightly and everything should be fine."

So which end is it? Plus, where do I get a spanner wrench?


Astronomics told me the same thing, but I did not see a ring at the focuser side, so I loosened the objective side as LLEEGE mentioned. I used a screwdriver, which is risky, but in my case a fingernail could not provide enough torque to turn the ring. As LLEEGE said, it doesn't take much - just a slight movement to correct the problem.

Please be careful - you might want to send it back to Astronomics if you are not comfortable using tools around the lens. As Mark pointed out, you can make a serviceable pin spanner with a couple of nails and a piece of wood; I've done that in the past for another optical assembly with success. Good luck --Keith

#7 gapalp

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Posted 04 January 2012 - 06:16 PM

Thanks guys. I will loosen the objective side and see what I can do without a tool or with a screwdriver.

#8 CapnRon

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Posted 04 January 2012 - 11:28 PM

I received my AT65EDQ in October and have only had a few outings with it, but I think I may be experiencing the same issue. This is a 30 second exposure, where I paid attention to focus and polar alignment set up, it is a cropped region from an image of M33. The 2 minute exposure of the same region looks nearly identical, but with brighter stars.

I believe I should contact OPT and get their opinion on this, but I thought I would ask here first.

thanks for looking.

Attached Files



#9 gapalp

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Posted 05 January 2012 - 10:58 AM

Looks like the same problem as mine and the others. I haven't tried the fix yet but will report back when I do.

#10 gapalp

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Posted 05 January 2012 - 12:14 PM

Just got done making the adjustment to the objective retaining ring. I had to use a screwdriver to loosen it since it was so tight. I tightened it back with my hand until it just touched the outer optics. All in all a fairly easy process, just don't let the screwdriver slip!

The next night I get out I will test then post the results. That may be tonight.

#11 David Ault

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Posted 05 January 2012 - 06:53 PM

After talking with several people about the triangular stars I got with my AT65EDQ I tried loosening the retaining ring on the primary optics first without any improvement. Both OPT and Astronomics thought it was the flattener ring that was too tight and I finally got a good description of how to access it. First, unscrew the focuser assembly from the scope (it just twists off). The flattener is in a separate assembly screwed into the main OTA. Mine was quite tight and took some force to unscrew. Once removed you should be able to loosen the flattener retaining ring just like the one on the primary optics. The retaining ring on my flattener was VERY tight, even when the scope was warm. I had to use a screwdriver to loosen it which also took some force and a lot of care to not touch the optics when it gave way. I must have gone a little too far and unseated the flattener as the ring gave way because I now see potato shaped stars (David B in NM suggested this was the cause).

Good luck with yours.

Regards,
David

#12 gapalp

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Posted 05 January 2012 - 08:16 PM

Thanks for the info. I am seeing the same results with triangle stars even after adjusting the objective side. I see it with 5 and 10 second exposures without autoguiding so I know it is the optics. I will try the focuser side next. If that doesn't work I will have to send it back to the vendor to resolve.

Did you ask the vendor to take yours back since you still have distorted stars?

#13 David Ault

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Posted 05 January 2012 - 09:49 PM

I purchased the scope from OPT and had actually started a return with them when David B in NM PM'd me and suggested I make sure the flattener was seated properly. I'm just about to test that now. If I get nice round stars I'll ask them to cancel the return tomorrow.

David B in NM just received his AT65EDQ and noticed that his Quality Control card was blank. I went and checked mine and it was blank as well, so you might check yours too.

Regards,
David

#14 gapalp

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Posted 05 January 2012 - 10:54 PM

OK. I adjusted the flattener retaining ring, twice actually. The first time I did it then mounted the scope and did some test images. I was getting potatoe stars instead of triangle stars, similar to David's description.

So I thought it must need tightening some more, maybe I loosened it too much. So I got in there again and tighted it more than hand tighten but not as much as a spanner wrench would (was using a screwdriver) or as much as it was from the factory.

Here are my current results:

10sec
5sec

I believe there is still some distortion, but it is about 90% better than what it was. Do you think I should continue trying to perfect this?

#15 David B in NM

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Posted 05 January 2012 - 11:00 PM

gapalp,

That looks very good to me even zoomed to 400 percent. Most stars really appear as almost perfect circles through my eyes.

I'd suggest taking a couple real images and see what you think before you make any re-adjustment.

David B in NM

#16 zerro1

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Posted 05 January 2012 - 11:25 PM

it looks like there might still be a small amount. obviously you're on the right track. that flattener is a chunk of glass, isn't it. One thing I did find on mine after quite a bit of use; the 4 screws in the bottom of the focuser mechanism came loose, caused some issues.

I've had mine apart for different reasons but never encountered these distortions that you guy's are experiencing. I had the cell completely dis-assembled and removed the flattener. When I re-assembled, I just "lightly snugged" the retainer ring's. enough to be certain it wouldn't shift but not so much to really put tension on anything.

#17 gapalp

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Posted 06 January 2012 - 10:29 AM

Yeah I notice a small amount of distortion left. I may have a go at another imaging run but if these 5/10 sec exposures are showing, surely longer, stacked images will.

I could make more adjustments to perfect it, but I am at the point of wanting to send it back. It is only a 3 month old scope. If one or two user adjustments doesn't fix it, what is the customer really supposed to do? I am waiting on the opinion of the vendor to see what they say.

#18 gapalp

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Posted 06 January 2012 - 10:59 AM

The vendor (Astronomics) responded feeling the images show I have the element tightened properly. I do trust their opinion in this as they are one of the best vendors I and others have dealt with.

The slight distortions I currently see in these recent images could be from focus/fogging up/ambient temp problems since I had to take the scope inside/outside several times last night while making the adjustments.

I will proceed with an imaging session without any more adjustments. I think I will be satisified with the results. It is a huge improvement over the triangle stars!

#19 David Ault

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Posted 06 January 2012 - 02:38 PM

No ammount of loosening or tightening of retaining rings or attempting to get the flattener seated properly removed my 'potato' stars. Maybe someone more experience than I could correct this, but I decided if it's so fiddly in the first place it's not the right scope for me at this point in time and with my experience. So, mine is going back.

Needless to say I'm a little disappointed, but I can't complain too much. I've gotten a crash course in optics and the overall learning experience should prove invaluable with the rest of my astronomy.

I hope the rest of you come away with more than just education ;)

Regards,
David

#20 jrcrilly

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Posted 06 January 2012 - 03:05 PM

I hope the rest of you come away with more than just education ;)

Regards,
David


Me, too. It's really a sweet little imager when working properly (mine required no fiddling).
sample

#21 gapalp

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Posted 06 January 2012 - 03:25 PM

Sorry David you couldn't get the results you wanted. Mine could have went either way. I didn't have any experience in this stuff either. Do you plan on exchanging or going with something different?

Jrcrilly, that's about the way my stars look now so your image validates where my optics are at with the adjustments. Thanks for the sample.

#22 David Ault

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Posted 06 January 2012 - 04:35 PM

I was definitely sorry to see it go. The pictures I had taken with it had lots of potential. I haven't decided on exchanging it for another AT65EDQ or going with something else for wide fields. I think if OPT can confirm that it has been quality checked, or check it themselves before shipping it, I'll consider another one. They guys from OPT were very nice and said I could wait until it arrived (next Wednesday) to decide if I just wanted to return it, exchange it or try something else.

Regards,
David

#23 CapnRon

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Posted 06 January 2012 - 09:40 PM

I am waiting to hear from OPT as to what they think I should do with mine. They are looking at the pictures I sent them to see what they think the issue is.

thanks for the heads up on this.

#24 zerro1

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Posted 06 January 2012 - 10:39 PM

I really suggest that you guy's give them a shot at getting it straight. These are great little scopes with a nice FOV. If OPT or Astronomics or who ever you got them from can solve this for you, you will still be ahead with this scope. to get anything else that is a quad design with the native flat field it's going to cost much more. If you get another small scope that requires a field flattener to be added to the focuser; now you have extended length and added leverage to cause you other issues like a sagging focus mechanism. I understand the frustration of trying to improve your results, and fighting an optical issue is no fun. You're drawn to the flaw every time you open up photoshop. I've battled issues with the QHY9 and had to ship it to the maufacturer in china no less. I lost some really nice data to the flaw that is now repaired...but now the sky is being completely "un-cooperative", and I may not get anymore shots on the targets I want until next year. It's all a learning experience!

here is an example of data gathered with two different CCD's on the AT65EDQ. One was a QHY8, the other was a QHY9. Sal(SGT500) processed the data from the QHY8 and then I added the QHY9 data to it after the fact.

Attached Files



#25 CapnRon

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Posted 09 January 2012 - 07:57 PM

OPT has vowed to help me resolve the possible issue with mine. They have first suggested that it might be a associated with focuser sagg and would like me to take a couple of pictures on either side of the meridian. I think this is a reasonable possibility as I have an 8300M SBIG, filterwheel, slim OAG and a Lodestar hanging off the focuser. Although, I only have to back it out about 5/8" to achieve focus. Still I will take the pictures once our skies clear (we need the rain).

I very much want to keep this scope (or its equivelant) because I do like the relatively wide field views it provides and ease of tracking on the CGEM mount.

Happy New Year all,
Ron






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