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Re:M 26

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M 26 was created by Mohamed



Imaging telescope / lens Celestron Schmidt-Cassegrain (SCT) 8"/2032 mm 8SE
Imaging camera Canon T3i (CMOS)
Mount Equatorial Sky-Watcher HEQ5 Pro
Guiding telescope / lens Celestron Schmidt-Cassegrain (SCT) 8"/2032 mm 8SE
Guiding camera ZWO Optical ASI120MM Mini (mono) (CMOS)
Filters ZWO Optical Luminance (UV/IR block) 1.25"
Accessories Off-axis guider ZWO Optical, Focal reducer Celestron 0.63x, Filter wheel ZWO Optical 1.25", Automatic focuser JMI MotoFocus+
Processed with GIMP (GNU Image Manipulation Program) 2.10.20 (revision 1), Astro Pixel Processor 1.082, PHD Guiding (Stark Labs)

ISO 800
Lights (filter Luminance) 28 x 90 sec
Total lights integration time 42:00 min

Date Tue Oct 6th 2020
Seeing 3 / 5
Transparency 3 / 5
Sky Darkness #4 Rural/suburban transition - 6/9
Binning 1x1
3 years 5 months ago #61250
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Replied by Gonzothegreat on topic M 26

nice work, very nice.
3 years 5 months ago #61253

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Replied by Mohamed on topic M 26

Thank you, but I was looking for rounded stars like your images. It seems that I'm still struggling with it. I found that Pixinsight (trial) actually round the stars, but this is due to an algorithm that actually alters the stars itself, and I didn't like that. I want to be able to get as round as possible in the widest area possible. Any advice on how to achieve that?

Is it the polar alignment? the accuracy of the guider? the mount mechanics?

PS: This is my 1st time trying PHD as a guider
3 years 5 months ago #61260

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Replied by Gonzothegreat on topic M 26

To get round stars, it's a combination of a lot of things I think.
mount accuracy, is there any backlash? Can you fix it, or minimise it?
telescope balanced?
polar alignment, try to get the best you can with the Kstars PA tool

imaging train must set correctly, back-focus all good?
Focusing
do you have a field flattener?
guiding, are you using the multi-stars option?


Spend some time on the mechanical part first, make sure everything is sound and working as it should. I did tune my mount, I took everything apart and changed some dead bearings etc... I have a post about it somewhere here.

Then spend some time on the telescope part.
and finally, on the software side.

Here's a very good youTube channel with tons of tips www.youtube.com/c/CuivTheLazyGeek
3 years 5 months ago #61261

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Replied by Daniel DeSclafani on topic M 26

If you are trying to get round stars then first look and try to diagnose the image to get you to a starting point.

To me that looks like could be a tracking error simply because all of the stars seem to be going in the same direction. I am also seeing what looks to be tilt. Diagnosis takes time, so don't get discouraged. I was put on pause for over 2 months fixing and diagnosing issues....also, I would upload your image to astrometry.net and figure out which way is North, east, south, and west.

Direction of trailing means:

- north-south: polar alignment problem

- east-west: tracking problem

- in between: a combination of problems

- radial: unflat field or coma

- tangential: movement in the camera mount or field rotation from poor or nonexistent polar alignment

These are just *some* possabilities. However, it is a good starting point.
Last edit: 3 years 5 months ago by Daniel DeSclafani.
3 years 5 months ago #61282

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Replied by Mohamed on topic M 26



Thank you for the YouTube link and other information. This is really helpful

I've already purchased the HEQ5 mod kit belt and also a higher quality replacement bearing set. I just didn't install them as the mount is few weeks old, and I don't know if you recommend replacing them now or wait...
3 years 5 months ago #61283

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Replied by Daniel DeSclafani on topic M 26

I wouldn't touch the bearings right now. Go ahead and do the Rowan belt mod, however, be gentle. It's easy to pull off any connectors from the board.

Bearings would be last on my list. I do not plan on changing mine until it has been used for a good while. Like a few years or so, if at all.

Rowan belt mod and then look into adjusting the worm gear meshing. Be gentle with it though and work in small increments. Astro baby has a guide for it. Google astro baby HEQ5 worm gear mesh.

That's as far as I would go with touching the mount. There really should be no need to do much more, you do not want to make it worse than it is by doing something incorrectly.

Aa I said first, try and find yourself a starting point. Solve the image and figure out which direction is which.
3 years 5 months ago #61284

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Replied by Mohamed on topic Re:M 26


I did upload the above image into astrometry.net and it was resolved successfully, but I couldn’t find any information about the direction and analysis of the distortion... can you please explain the role of astromerty.net as a first step?
Below is the image from astrometry.net showing RA/Dec



Thank you
Mohamed
Last edit: 3 years 5 months ago by Mohamed.
3 years 5 months ago #61285
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Replied by Daniel DeSclafani on topic Re:M 26

I just solved your image.

From astrometry "Orientation: Up is 234 degrees E of N"

UP is 234 degrees East of North. So therefore this trialing is east - west...looking at what I had said above it looks to be a tracking issue. So the Ra Axis.

The first thing I would do is make sure the OAG and all other connections are secure. However, since you have an OAG I would doubt that it is a flexure issue.

First thing I would do it adjust the worm gear meshing, you can do it for both RA and DEC.

Once the Rowan Belt mod comes in I would assemble it asap.

Solve this tracking issue first. It should be fairly easy to figure out. Also make sure your tracking rate is set to sidereal.

After the tracking issue figure out where the tilt is coming from. My guess is going to be the T adapter for the canon camera.
3 years 5 months ago #61301

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Replied by Mohamed on topic Re:M 26



Thank you Daniel so much for this tip and this checklist. I will install the belt mods ASAP and test again.

I just wonder what astrometry.net verbose would be to conclude it is North-South trailing?
3 years 5 months ago #61305

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Replied by Gonzothegreat on topic Re:M 26

This is the post where I took the mount apart.
The following user(s) said Thank You: Mohamed
3 years 5 months ago #61308

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