mackiedlm

I have been imaging with my LX200 GPS 8" for a couple of years using a 0.8ff/fr and a ASI2600mc. While not brilliant the stars were ok and acceptable to my eye and I produced some OK images (for that set up!)

I then swapped the meade electric microfocuser for a crayford, to allow for autofocus. This required significant movement of the primary mirror to reach focus.  Right away with this focuser my stars went crazy with bad shapes (coma?) accross the entire field. I assumed it was a tilt issue from the new focuser and worked to resolve that with no success.. I then refitted the meade focuser but the problem is still there.

Images to illustrate

These are un debayered single images of 180s with a simple stf stretch apprlied. The PI Abberation Inspector images show the problem more clearly.

There may be some tracking error in these images but the starshape issue is seen even in 5s images so this is not tracking. 180 s images were my normal exposure previously and did not have this issue.

I did star collimation before these images and thought I had done a reasonable job. But I would not claim a high level of competence in collimation. I know the focus looks soft but it was done with autofocus in APT (I worked out how to get that going on the meade focuser) and I think it is just the abberation that makes it look that way.

Connection to the scope is with a 2 inch nosepiece as its not possible to do a screw connection. And that nosepiece connection was working fine before I messed with the focusers.

Image 2 is after a rotation of the camera and FF/FR in the eyepeice holder and shows that the abberation remains the same relative to the target while the FOV rotates. This suggests to me that any issue is scope side of the connection between the camera and the FF/FR. I guess its possible there could be tilt between the nosepiece and the eyepiece holder but I doubt if the abberation would remain as unchanged if it was that. I did try ensuring a good alignment and again, it was not present before I removed and the replaced the meade focuser.

This is leading me to consider that the issue could be either a collimatio issue or tilt of the primary mirror, although I have read that that is highly unlikely.

I would greatly appreciate any guidance on where I should look to resolve this.

Can we stay away from backfocus, questions of which FF/FR etc because the camera, reducer, nosepiece system has not been changed or seperated from when I was getting acceptable results during the winter.

Thanks

David

That is a wonderful image. Something i've not seen before.

And as a Scotsman I just have to love it!!!

This is a 3 panel Mosaic within Cygnus. It is around 2 hours per channel/panel and is processed in a dynamic HOO palette.

Sharpstar 61EDPHII, QHY163M, ZWO 7nm Ha and Oiii

DHoo_L_reducedIC.tif

that is a lovely image with super detail.

Super view. Well done.

I really like that. Well done.

Thats really nice. great structure in the main nebulae.

1 hour ago, Fegato said:

Very nice!  I've just shot an 8 panel mosaic with M81/2 in the bottom left corner, aiming to catch the full extent of LBN683 (a huge area of IFN). I'll be very pleased if I can keep the galaxies down as well as you have - any tips gratefully accepted! 

Thanks Robin. So it was really all about careful masking. I used PI's game script to produce the initial Gradient edge mask then trial and error with HT and convolution on the mask to get something that preserved the galaxies without producing artifacts at their edges. I also made the mistake of not including the two smaller galaxies NGC2976 and NGC3077 in my initial masks. And i did not keep an eye on them as the processing continued until, at the end, they were totally blown out and stood out like sore thumbs 😂. So I had to basically go back and start again!

Good luck, I look forward to seeing your mosaic - are you doing it with the RASA? That will be brilliant.

1 hour ago, Catanonia said:

Really nice and you got a good amount of the IFN there is a large FOV. It really shows the extend of the IFN in this region   

Love the colours too, not over done which is nice.

Did you image the galaxies separately or were they in the same subs ?

Very nice. 

Thanks for that. No, not imaged separately, just one set of subs and very careful masking. I have a set of subs taken at a higher FL with better detail in the galaxies and I'm thinking i may try to graft them into this.

I imaged this area about a year ago with my 80ED but was never that happy with the result. So I gave it a go this year with my 61 EDPHii.

This is 6 hours of 180s subs with the ASI2600mc and the L-pro filter

After almost exactly two months since my last clear sky I got my first image of 2023 on 13 February!

This is a target I've wanted to do for a long time but its very low for me and by now its getting late in the season. And then the clear nights were not clear as long as forecast. So this is only 3.5 hours of integration and it needs much more. But that will not happen this season!

ASI2600mc, Sharpstar 61 EDPHII Altair L-pro.

Thanks for looking.

Fantastic image, Such depth and detail.

Both are super images but i do prefer the second, the blue grey shading to the browns gives more sense of depth.

Lovely image, great colours and detail.

thats an excellent image. ncely done.

I really like that. the colours and definition in the cores are excellent

I came accross this data while filing everything from my pre-christmas spree of several nights imaging. I had forgot all about it.

Its only 4 hours, captured in less than ideal conditions (99% moon) with only an L-enhance. I think its come out ok considering. The Rosette Nebula sits above the RHS of this and I plan to do a 2 panel of it.

80 x 180s, Sharpstar 61 EDPHii ASI 2600mc and Optolong l-enhance. processed in Pixinsight using Blanshans HOO normalisation method.

thats lovely. The tadpoles show very well swimming in their "Blue lagoon"

Thats superb, never seen the two in one FOV before. Excellent

thanks @Vlaiv, I've just posted it up so you can take a look if you are interested. The overlap does cover the pillars area in NGC7822 and i dont think they hare significantly degarded - as you have explained/

This combines a panel taken with my 61EDPHII (275mm FL) with and my earlier 2 panels made with my SW 80ED (510mm). It was intended to show the cosmic question mark but unfortunately the 80ED panels cut off too much for it to show well. I started a thread on Processing Tips asking about which would bethe best panel to register against (thanks @vlaiv)  This one was done with register against the middle 510mm panel so, as Vlaiv explained, the lower panel may look a little more blurred. i'll probably go back and do it again registering the other way.

Its Around 3.5-4 hours per panel all done with the 2600MC, L-enhance and processed using Pixinsight and Bill Blanshans HOO normalisation method.

thats asuper image - nicely done.

31 minutes ago, vlaiv said:

If you choose panel shot at 510mm FL as a reference, then you run a risk of part of image being visibly more blurred than the rest of it - 275mm FL panel will not look as nice as others when enlarged to their size.

If you choose 275mm FL - then whole image will be "smaller" in size - objects in it will be of a smaller size when viewed at 100% zoom level. It will look the same when you fit it to screen - then either of them will be the size of screen so objects in each image will look the same size (by each image I mean one registered to 510mm FL panel and one registered to 275mm panel).

Although I know what I meant, I'm not sure I was particularly understandable, so I'll reiterate in bullet points.

Registering to 275mm panel:

- smaller total size of image in pixels

- smaller objects (compared to other option) when viewed at 100% zoom, but equal size when viewed "fit to screen"

- whole image will look equally sharp when viewed at 100% zoom

Registering to 510mm FL panel:

- larger total size of image in pixels

- larger objects at 100% zoom level

- risk of part of image looking visibly more blurred then the rest of it (panel that was shot at 275mm will look more blurred then the rest).

Thanks Vlaiv - thats exactly what I needed!

As a follow up question, what happens the second case (registering to the 510 panel) in the overlap area. I the image I am working on there is an overlap area which holds some quite small detail. Will the 275mm panel significantly degrade this area of detail? I have already processed the image this way (registered to the middle 510mm panel) and i am relatively happy with it. I think the lower panel (as you indicated) does look more blurred but as there as not much in that panel I was willing to live with, I'll post that image up in the DSO page.

Thanks again

I have 3 panels for a mosaic. All taken with the same camera but 2 panels (top and middle) at 510mm FL and 1 panel (bottom) at 275mm FL. I will build the mosaic in Pixinsight using Photometric Mosaic Script  and can do that without problem.

Unfortunately I dont really understand the whole resolution/upsampling/downsampling business well enough so am struggling to decide which panel to use as the reference image such that I dont lose any detail or resolution in the process.

Any help would be appreciated

This is the next image from my haul of last week.

It is 4 hours of 180s subs with the sharpstar 61EDPHii, ASI2600mc, L-enhance filter

Processed in PI using Blanshans HOO normalisation method.