46 replies to this topic

[feygan]

Hey guys,

 

I spent the last 3 nights of clear skies fidgeting around with the backspacing of my William Optics Zenithstar 61 with the Flat61A.

 

I cannot get a flat field, no matter how hard I try. I always seem to have elongated stars in only one corner of the image.

 

My methodology was as follows:

1) I suspected wrong backspacing from the flattener to the camera sensor. I set the variable flattener at 12.9mm as indicated by the manual. I started to move the camera 0.1mm back and forward for at least 30 times in each direction (total 60 adjustments; 3mm in, 3mm out), each time refocusing with the bahtinov mask. I found absolutely no improvement.

 

2) I suspected camera sensor tilt so I started to rotate the camera relative to the flattener. The elongation moved as the camera was rotated. I've attached two small gifs (stretched) as I was rotating the camera. You can clearly see how the light pollution changes orientation.

 

 

My current setup is WO ZS 61 -> Flat61A -> Nikon T Ring -> Nikon D5300.

 

I'm starting to suspect some sort of tilt in the optical train. How can I tackle this?

 

PS: It dug around my old pictures with a Sony A6300 with a different T ring, same issue. I can safely rule out the camera or the T ring.

 

PSS: The markings on my flattener differ from reality. 1mm on the flattener is not 1mm measured with a digital ruler. Now the question is, do I trust the flattener markings or do I use a ruler to measure backspacing?

 

Edited by feygan, 24 April 2020 - 11:17 AM.

[OldManSky]

If the distortion moves as you move the camera (as you've stated), then it *is* tilt.  The tilt likely comes from the camera mount point/sensor not being flat to the imaging train, or some sag in the focuser.

Sag in the focuser is sometimes easier to fix -- tighten up the tension screws a bit, that will often get rid of most of it (even if it makes your focuser a little harder to turn).  If it's camera mount point/chip, that's tougher.  There are "tilt adapters" you can buy.  But the first thing to check is any sag or off-straightness in the camera's t-ring.  Some of them fit a bit loosely, so the camera can wiggle a little, and some of them (especially the cheaper ones) simply aren't made so everything is parallel.  You want nice, tight fit that is also nice and straight.

 

As for the scale on the flattener...got me.  I never measured mine (I used to have the Z61 and its flattener, now I have the Flat6AIII for the GT71 and ZS103).  On all the scopes, I adjusted using test images until I got a nice flat field, then noted the setting for repeatability.  It doesn't matter if the flattener says "9mm" but it's really 8.7mm, I just have to go to the reference point and it's all good

[feygan]

Thanks for the suggestions. I just tested now:

- tightening/loosing up the focuser knob

- tightening/loosing up the flattner knob (which controls camera orientation)

- inspected the t-ring

 

No improvements so far.

 

Any other ideas that I could try?

[timmbottoni]

If you look at the flattener, it rotates if you loosen the thumbscrew.  Check all of the little plastic/nylon slotted inset screws and make sure they are all about the same snugness.  They are soft so don't overtighten them, of course.

 

If there is wobble in the focuser tube itself there are two tension allen inset screws, but if I remember one is under the clamp.

 

Timm

[OldManSky]

Look on page 4 of the Z61 user manual ( https://williamoptic...wner_Manual.pdf ).

Item [13] shows two 2mm screws on top of the focuser that adjust the draw tube tension.  Make sure those are snug to the point that there's no wobble or sag in the focuser, but the focuser still moves easy enough in/out.

Then further down on page 7, there is a photo of the underside of the focuser, where it shows the two 3mm screws on the bottom of the focuser -- these can also be adjusted to snug up any play or sag in the focuser.

 

Hope that helps...

[feygan]

Thanks for your replies. 

 

What I've tried so far:

1. Moving the camera back and forward using the adjustable ring on the Flat61A. I moved it 0.1mm at a time starting from 10mm to 15mm (recommended is 12.9mm)
2. Changing the camera and the t-ring adapter. I've used both a Nikon D5300 and a Sony A6300
3. Adjusting (loosing/tightening) the nylon screws on the Flat61A that control how stiff the orientation mechanism is
4. Adjusting (loosing/tightening) the 3mm focus screws on the Zenithstar61 itself in order to rule out any mechanical tilt. I've tried with both sets of screws, those below the scope, and those below the collar (above the scope).
5. Tested with really short exposures, 1-3 secs inside the house to rule out any jerk by the guiding mount. I've also tested it with the scope sitting directly on the ground in order to rule out possible tension in the mounting system. I've also tested it with the collar attached/removed.

I've found no improvement yet with any of these techniques. The top-left side always has coma.

 

I've had a chat with WO support and they recommend sending it back for inspection. I'm trying to find a good cost effective courier to ship it to Taiwan at the moment.

 

I'll keep you posted

[Rotciv.greene]

I too have had this exact same issue with this scope. I’m almost certain that your issue is slop in the draw tube. I say this because your symptoms mimic those of my Z61. Also, based on your post, you seem like a thorough person and I would assume you’ve checked your math 30 times. For me, it came down to placing strips of PTFE tape (not plumbers tape) on the draw tube to fill in the gaps and make the tube straight. It does eventually break in a bit so you may need to add more over time. I thought about upgrading the focuser for this reason, but couldn’t justify the cost seeing as it was half the cost of the scope itself. This page has a link to the tape. Hopefully this can help!

http://www.eyesonthe...provements.aspx

Edited by Rotciv.greene, 11 May 2020 - 06:21 PM.

[astrobrian]

Have you been able to resolve your issue yet?

 

I am seeing something very similar using the ZS61 and the newer Flat61-R reducer that happens across both my cameras.

 

In my case WO believes it is the reducer and I am getting shipped a flat61a to test with as a comparison but this thread does not get my hopes up.

 

They also had me take images without the reducer and that (while not flat) didn't look tilted and that required my focuser tube to be very extended.

[feygan]

I wasn't able to fix it. I ended up sending the scope back for inspection and I'm still waiting for them to respond / send it back

[astrobrian]

Well if you could post your update when they do respond that would be awesome. If I end up having the same issue with the flat61a I suspect I will need to go down the same road as you.

 

Did they have you take images without the flattener attached? Here is what mine showed unflattened which had them initially rule out the ZS61 causing my issue.

These images don't seem to have too much tilt to me.

 

 

[feygan]

Nope, they didn't ask me to test it without the flattener. 

 

I ended up sending the scope alone without the flattener due to some bad customer experience from the shop I bought the scope. 

 

If the scope turns out to be fine, I'll have to send the flat61a separately and wait 2+ months again.. Fun times

[feygan]

I have serious concerns regarding the quality assurance from William Optics's internal team. Seems like it's a hit and miss. Some people have no problems, yet others have serious comma. You'll find at least 10 posts on cloudy nights alone with this issue with no clear solution. If you start to go down the rabbit hole and search astrobin for the ZS61, you'll find that at least 50% of the images have comma in one corner.

 

If I start to calculate how many hours of frustration I've wasted trying to correct this, I could have bought the most expensive scope on the market.

[astrobrian]

I hear you on the time spent. At this point I have spent about 5 clear nights sitting next to my rig for 3 or 4 hours taking different shots making backfocus/equipment changes trying to dial these in.

 

I am still fairly new to this so I originally assumed it was me doing something wrong and I had spent an equal amount of time or more reading forums and trying to troubleshoot (and I assume it still could be since I somehow missed the focus tension screws that I will have to try next). 

 

I recently saw on Agena that they are coming out with a new version of the  ZS61 which incorporates the SpaceCat mounting foot. I wonder if there are any other changes with the new version which would make it that much more expensive. 

 

https://agenaastro.c...se-a-z61ii.html

 

Ill let you know what comes of the flat61a I am being sent vs the flat61r reducer I have the same problems with.

Edited by astrobrian, 15 June 2020 - 09:02 AM.

[Epox75]

 

PSS: The markings on my flattener differ from reality. 1mm on the flattener is not 1mm measured with a digital ruler. Now the question is, do I trust the flattener markings or do I use a ruler to measure backspacing?

 

Ehm... did you check the markings on your digital ruler?

[milkychris]

I too have had this exact same issue with this scope. I’m almost certain that your issue is slop in the draw tube. I say this because your symptoms mimic those of my Z61. Also, based on your post, you seem like a thorough person and I would assume you’ve checked your math 30 times. For me, it came down to placing strips of PTFE tape (not plumbers tape) on the draw tube to fill in the gaps and make the tube straight. It does eventually break in a bit so you may need to add more over time. I thought about upgrading the focuser for this reason, but couldn’t justify the cost seeing as it was half the cost of the scope itself. This page has a link to the tape. Hopefully this can help!

http://www.eyesonthe...provements.aspx

I agree, make sure you tighten the focuser draw tube lock screw.  I keep a lot of tension on mine to keep it centered.

[Polecat2]

Hello everyone. My first post on this forum. I also have a Z61 and the Flat 61R. I received an email from Agena this morning that amounts to a recall of the Flat 61R. Scott from Agena advised me that WO had notified them of a problem that could not be corrected and recommended that I return my Flat 61R to swap for a Flat 61A and a refund for the difference in cost. He didn’t specify the problems but as I read this thread, I suspect that I know what the issue is. I’m still a newbie in astrophotography but I’m now realizing that I have also seen some very slight elongation in a corner at times. I initially blamed it on my inexperience. I also own WO’s micro4/3 camera adapter and had a terrible time getting it to work with my Olympus cameras. I’ve replied to Scott’s email with a request for more information on the topic so I’ll wait to see what he has to say. 

[Hypoxic]

Exact same problems here with the exact same setup. Send the scope back (x2), send the new flattener back, send the guide scope back... the problems persist. The only thing I've purchased from W.O. that actually works is a dovetail plate.

 

Personally, I'm dropping these guys, they have issues.

Edited by Hypoxic, 02 July 2020 - 11:05 AM.

[CloudySky420]

I too have had this exact same issue with this scope. I’m almost certain that your issue is slop in the draw tube. I say this because your symptoms mimic those of my Z61. Also, based on your post, you seem like a thorough person and I would assume you’ve checked your math 30 times. For me, it came down to placing strips of PTFE tape (not plumbers tape) on the draw tube to fill in the gaps and make the tube straight. It does eventually break in a bit so you may need to add more over time. I thought about upgrading the focuser for this reason, but couldn’t justify the cost seeing as it was half the cost of the scope itself. This page has a link to the tape. Hopefully this can help!

http://www.eyesonthe...provements.aspx

 

I am still diagnosing a tilt issue with my Zenithstar 61. I just bought some PTFE tape to try this solution. How do you remove the focuser in this scope?

[CloudySky420]

I am still diagnosing a tilt issue with my Zenithstar 61. I just bought some PTFE tape to try this solution. How do you remove the focuser in this scope?

So in case anyone in the future reads this, all you have to do is simply unscrew the objective lens from the focuser and loosen the two 3mm bolts on the bottom of the focuser. After you can simply take the focuser wheel off and pull out the tube.

[Kevin_A]

I just bought the Zenithstar 61 V2 and it too has a lot of tilt in one corner.

I have tightened up the tension screws and will re-check tonight to see if it helps.

This should not happen with a new scope and FF.

Anyone have any resolution from WO yet?

[feygan]

I sent my scope back in May (almost 5 months ago) for warranty. Due to some logistical nightmares I still haven't received it back, so no updates.

Edited by feygan, 21 September 2020 - 10:35 AM.

[micky7890]

Exact same problems here with the exact same setup. Send the scope back (x2), send the new flattener back, send the guide scope back... the problems persist. The only thing I've purchased from W.O. that actually works is a dovetail plate.

 

Personally, I'm dropping these guys, they have issues.

I agree 100%. I wish I had come across this thread two weeks ago. I wasted at least 60+ hours troubleshooting this elongated star crap with the Z61 scope and flattener with no improvements. I tried everything everyone has described here, different cameras, different flatteners, dozens of spacer combinations, I mean, what a disappointment. I kept hope since several people have achieved great results with this scope but it looks like quality control is lacking and the probability of getting a dud is high.

[Hypoxic]

I agree 100%. I wish I had come across this thread two weeks ago. I wasted at least 60+ hours troubleshooting this elongated star crap with the Z61 scope and flattener with no improvements. I tried everything everyone has described here, different cameras, different flatteners, dozens of spacer combinations, I mean, what a disappointment. I kept hope since several people have achieved great results with this scope but it looks like quality control is lacking and the probability of getting a dud is high.

I honestly feel really bad for you because I went through the exact same frustrations. I tried SO hard to hold out, night after night after night, hoping it was just stupid me and not the equipment. But then I received a WO 50mm guide scope on top of my existing problems that had astigmatism so bad that it was unusable, and then the new Flat61R which was recalled before I even received it in the mail. It was time to call a cat a cat. 

 

I've since gone with TS and everything I've purchased works as advertised; couldn't be happier.

[feygan]

I honestly feel really bad for you because I went through the exact same frustrations. I tried SO hard to hold out, night after night after night, hoping it was just stupid me and not the equipment. But then I received a WO 50mm guide scope on top of my existing problems that had astigmatism so bad that it was unusable, and then the new Flat61R which was recalled before I even received it in the mail. It was time to call a cat a cat. 

 

I've since gone with TS and everything I've purchased works as advertised; couldn't be happier.

I don't know what happened. When I joined the astrophotography hobby, William Optics was highly regarded in the community (probably still is)..

 

Regarding TS, I've heard multiple people being happy with their products. There is a line from TS that is made in the same factory as the WO scopes, yet don't have the defects.

[Kevin_A]

Hello everyone. My first post on this forum. I also have a Z61 and the Flat 61R. I received an email from Agena this morning that amounts to a recall of the Flat 61R. Scott from Agena advised me that WO had notified them of a problem that could not be corrected and recommended that I return my Flat 61R to swap for a Flat 61A and a refund for the difference in cost. He didn’t specify the problems but as I read this thread, I suspect that I know what the issue is. I’m still a newbie in astrophotography but I’m now realizing that I have also seen some very slight elongation in a corner at times. I initially blamed it on my inexperience. I also own WO’s micro4/3 camera adapter and had a terrible time getting it to work with my Olympus cameras. I’ve replied to Scott’s email with a request for more information on the topic so I’ll wait to see what he has to say. 

Did you ever get this resolved or an answer as my 61A flattener is tilted too....