M104 - Sombrero Galaxy

[browndog (Ian)]

Image taken with C8 SCT with 6.3 focal reducer.

Autoguided using PHD and an 80mm achro + webcam. I used a 1.25" UHC-S filter to reduce light pollution.

12 x 5min subs with an unmodified Canon 350d @ ISO800 and then stacked in DSS. Post processing in PS.

This is my first image of the Sombrero galaxy. Any comments greatly appreciated

[Lester]

Nice image of M104 Ian.

I presume this image isn't cropped at all. The stars look sharp at the centre and top of image, but around the edge the rest of the stars are slightly distorted.

Either something isn't square with the focus point or collimation may be slightly out.

If the image is cropped, that may explain what I am seeing.

All the best.

[theodog (Jeff)]

I agree with Lester, a nice image of M104.

Could the star 'problem' be a combination of mis-collimation and slightly off polar alignment?

Still great image of 104.
Well done.

[Alchemy (Clive)]

thats one id like to do myself later, the galaxy is nice and sharp.
have a play with the different varieties of stacking in dss, sometimes median works if theres a little bit of movement, id say try them all and pick the best one to work with, you would be suprised at the difference on occasions.

[Ric]

Very nice Ian, M104 looks fantastic just hanging there amongst the stars.

Cheers

[browndog (Ian)]

Thank you everyone for your replies. Greatly appreciated.

As suggested by Lester and Jeff, I checked my collimation and it was not properly aligned.

So after a bit of research I decided to collimate my SCT...! Not as hard as I first thought and I think that I got it right. Still need to finish processing the images that I took after collimation but on initial inspections they results look pretty good.

[edwardsdj (Doug)]

The Bob's Knobs from Bintel are only about $30 for the C8. They really make collimation easy. I touch it up before mosts observing sessions now. I used to be so nervous about holding a screwdriver in front of the corrector. Now it is easy

[browndog (Ian)]

Yes - I need to get some of those "Bobs Knobs".

Holding a screwdriver near the corrector plate and in the dark... seems a recipe for disaster.

[edwardsdj (Doug)]

It is important to speak with them over the phone before ordering the knobs as there are two types of C8 with different knobs. I didn't know this and am glad I rang up instead of just ordering on line. The guy I spoke with knew all about it, asked me something simple about the scope (I think it was to do with the existing collimation screws being phillips head or flat head) and the right knobs arrived a couple of days later.

It is important to keep all three collimation screws reasonably tight so that it holds collimation. The knobs make this easy too as they are plastic and you get a feel for the tension with your fingers. It was really hard to get them all tight with the screwdriver and factory collimation screws.

You have to find a firm tension on all of them that feels like it's going to hold without being loose or too tight.