Jump to content

Banner.jpg.b89429c566825f6ab32bcafbada449c9.jpg

Coma corrector artifacts


Many

Recommended Posts

Hi everyone, I just get a Newtonian 150mm F4, also come with a GSO coma corrector, in my first setup I didn't get the correction that I was looking for (issue at the corners of the pics),  later I change the configuration (distance of the corrector to the camera) and the problem was fix in a 95%, very happy.

So yesterday in my last test I do subs of 60 sec of Zosma (star in leo, SAO81727)

All good and a lot of coma in my photos, later I made some changes in the optic train, put the coma closer to the the sensor and finally round stars.

The first set of photos shows something like a star with a blue halo,  and my last photo when finally my problem was solved, the object disappear, 

The question is if this can be an artifact product of the coma corrector?

The artifact photo and the no artifact photo is a 2 minutes difference in time.

Thanks for your inputs.

Attach two photos

_DSC0055.jpg

_DSC0061.jpg

Link to comment
Share on other sites

Welcome:)

The two frames do not cover the same field of view and the second one has star trailing, so it's not really possible to tell.

On my 'phone, I see the second frame having the blue halo. 

Keep the cc to sensor spacing as close to 75mm as possible. I think at 600mm and judging by your photos, you will need to increase it. With the gso on a 150mm f5, we were closer to 80mm before the corner stars tightened.

The issue with the gso cc is that it increases the effective focal length of the telescope. Not really what you want with a nice fast f4. If you have a choice, go for the WYSIWYG GPU.

Cheers and HTH.

 

 

 

 

Edited by alacant
Link to comment
Share on other sites

Hi, thanks for your advice, that is true, some difficult finding the correct distance, but I think I go it finally. Still confused me that at 5 cm from the sensor produced this funny fake star and at 7cm it is gone. Just to add, the first time that I used the GSO, I do with the 5mm ring that coming with the GSO, same exposure, same target, lot of coma, but not this fake star. 

You mentioned another coma corrector, but when I trying to search for it, skywatcher coma is the result, is that one you suggest?

Cheers from Bonaire

Link to comment
Share on other sites

9 hours ago, Many said:

skywatcher coma is the result,

That is a version of the real thing marketed by Skywatcher. Get the proper version.

9 hours ago, Many said:

I do with the 5mm ring that coming with the GSO,

That is a m48 to m42 adaptor. I'd recommend losing that adaptor and using m48 throughout. If you are serious about the AP thing, I'd recommend you get a set of m48 extension rings

Link to comment
Share on other sites

https://www.teleskop-express.de/shop/product_info.php/language/en/info/p6706_TS-Optics-NEWTON-Coma-Corrector-1-0x-GPU-Superflat---4-element---2--connection.html

 

This is the coma corrector in question.

It's quite expensive but I took the plunge and have it on my tsoptics f4 8inch astrograph and the results are very rewarding.

Alacant helped me to fine tune some design issues on mine which turned out brilliant too.

Added pic is latest result.

Stu 

174431227_10216267350910089_1489360400118798061_n.jpg

Edited by Stu Wilson
  • Like 1
Link to comment
Share on other sites

Great picture, amazing. Tonight is going to be clear sky. I will do more test. 

Regarding the ghost star with blue halo, is just a reflection? Or a parasite light getting in the tube.

Cheers.

Link to comment
Share on other sites

27 minutes ago, Many said:

Great picture, amazing. Tonight is going to be clear sky. I will do more test. 

Regarding the ghost star with blue halo, is just a reflection? Or a parasite light getting in the tube.

Cheers.

If I'm honest..... I'm not sure.

But I'd seriously recommend the cc in question.

Which ota do you have?

Maybe you should consider the mods I did also.

Ie springs and collimation bolts.

 

Stu

Link to comment
Share on other sites

My OTA is a 150mm f4, I tested today and result was very good, the corrector is doing it job. I didn't had any artifacts and the small coma is really small.

I am very intriguing is this star with blue halo happened to other people and if is consistent with a reflection or something else, for me as a reflection is a bit difficult because was 40 pics, one minute each and of course the ota change position and the reflection will move on the frame,  what do you think.

Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
  • Recently Browsing   0 members

    • No registered users viewing this page.
×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue. By using this site, you agree to our Terms of Use.