Help needed with WO MiniCat 51 tilt issues - Forums

Topic starter

Perfect post

2 hours ago

Greetings! Looking for some help with my new WO MiniCat 51 and the tilt issues it has.

Imaging Setup:
WO MiniCat 51 WIFD
ZWO AM3
ASI2600MC Duo Air
ZWO EAF
Bin 1
180s exps

Test FOV:
Markarian’s Chain Widefield

Guiding:
.28 - .45 total RMS

Problem Statement:
My new WOMC 51 seems to have some tilt/aberration issues that I am having difficulty understanding. As a disclaimer, I am fully aware of the MC51 and corner issues. Based on other’s processed images, I believe I can do better. I’ve done some testing and I’m looking for comments on what I’m seeing and potential ways to address it.

📷 ASTAP_Original_Tri_Tilt.jpg1. The original process I did of about 40, 180s subs came out looking very mediocre for the my guiding numbers so I started digging in. ASTAP shows quite a bit of tilt. (Image was solved and showed a rotation of 270 degrees, Image Inspection was set at 90 degrees)

📷 ASTAP_Original_Oct_Tilt.jpg2. Switching to the Octagon it shows extreme tilt as well.

📷 ASTAP_Fixed_Tri_None.jpg3. I backed out all the tilt screws and reset them, this seemed to improve the tilt.

📷 ASTAP_Fixed_Oct_Severe.jpg4. The octagon option still shows severe tilt, but it is improved as well.

📷 ASTAP_Imaging_Tri_None.jpg5. After the tilt adjustment I did a short run of 20, 180s subs. I grabbed one of those subs and remeasured. The triangle method still shows almost no tilt, but it did regress some.

📷 ASTAP_Imaging_Oct_Severe.jpg6. The octagon shows the same.

📷 Original_ImgIns_Mosaic.jpg7. Here’s what the corners look like from the original capture and process of 40, 180s subs. Also, this process had drizzle enabled for some reason.

📷 Fixed_ImgIns_Mosaic.jpg8. And here’s the mosaic from the test run of 20, 180s subs after the tilt showed to be “almost none”, but these stars look way worse than when the tilt reported to be severe.

Questions:
1. Is there a better tool to understand the tilt of a system and to correct it? I’ve always used ASTAP and have found it to be reliable.
2. I image in B5 skies, and I believe that I can support 180-second subs with my darkness and guiding, but could these star issues be caused by oversaturation?
3. I understand that the “triangle” option for ASTAP Image Inspector measures a central part of the image, so should I be only using the “octagon” option to help correct how bad my stars are?
4. Am I misinterpreting these aberrations entirely and should be looking at other potential issues?

Apologies for the long read and appreciate any suggestions on this issue.

Jeramie

Well written Helpful Engaging

DavesView

1 hour ago

I take 10 sec to 30 sec images when correcting tilt. What works for me is a simple method:

1) take the image

2) open it in ASI FitsViewer

3) use the tilt identifier in FitsViewer

4) slightly push the big number(s) ( if one side has equal measurements, top/bottom/left/right) I push both screws associated with that side

5) refocus and reshoot and remeasure

NOTE: with the FitsViewer you have the luxury of looking at where it was via the previous subs instead of writing everything down and keeping a record of what you’re doing. I tried HocusFocus and ASTAP, but find this a simpler method that works for me.

I purchased the Z’Tilter for each of my ZWO cameras and can usually get it to less than 4% in a few measurements/adjustments. It is currently at 1% on my UltraCat108. With the accessories (everything known to man) on my RedCat51 III, I can’t get to the tilt tool built into the RedCat, hence the Z’Tilter for it. With the UltraCat108, I couldn’t get the STX (tilt tool) to work for two months. Went to the Z’Tilter and had it adjusted in 5 moves. With the focuser flop in my FLT91, I find that I often have to adjust tilt and can do so within a few adjustments prior to an imaging session. I always take a few test shots prior to imaging with any of my scopes.

Also, I would pick a better target than Markarian’s Chain for tilt measurements. Something with an even spread of stars like due north of M81. MC has too many distorted objects that are similar to stars.

Good Luck!

📷 TILT_TEST.png

Well written Helpful Respectful Engaging

Jeramie

Topic starter

Perfect post

1 hour ago

Great suggestions and I appreciate the help. Envious of your tilt!

You touched on one thing that I was trying to understand and that was the tilt plate. If a camera sensor has four corners, why would you only have 3 adjustment screws? I’m sure there’s a good reason for it.

Purchasing the new plates now. I’ve got another 2600MM coming today and I’m sure it will need similar adjustments.

Well written Respectful Supportive

Jeramie

Topic starter

Perfect post

45 minutes ago

Hey Dave- another question.

I completely overlooked the fact that the MiniCat has a 4-corner tilt adjuster built into the scope. Would you just use that one to adjust tilt over adding another device on the camera? Wouldn’t this make it more difficult to adjust?

Purchased one of the tilt plates for my C11 and looking forward to getting that in.

Jeramie

DavesView

20 minutes ago

I would have used the RedCat tilt tool on mine, but I can’t easily get to it. I have the rotator installed right after the M54 adapter. It’s the same four point adjuster as the Z’Tilter , I think. Never looked!

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