M64 Black Eye Galaxy

[Carole]

I started to image this after my original target disappeared behind the dome at 11pm.  This is my first attempt at this object and I didn't know how small it would be, but didn't want to waste the clear sky.  Also after the problems with the CCD cameras a few nights ago I wanted to use the DSLR to eliminate a problem with the scope itself.

35 x 300secs Modified Canon 450D CLS filter
Guided with QHY5 PHD and finder guider
Skywatcher Explorer 200PDS Newtonian
Captured in APT with dithering

With newly acquired coma corrector.  Unfortunately I wasn't able to get the spacing exact as the DSLR needed a thread adapter which was only 1mm but this put the spacing at 1mm too much.  Also focus was only just achieved at completely closed position of the focusser so it was a bit of a close thing.
The coma corrector is also a reducer so this brought the focal ratio down to F4.5

Close up


The full frame:


Link to larger file:
http://gallery.orpington-astronomy.org.uk/albums/userpics/10047/Black_eye_galaxy_35_x_5mins_DSLR_Newt_6-4-13_2nd_save.png

Carole

[Fay]

you did well Carole. change to see something we have not seen on here before. i think it would be too tiny for me to try that with my 120

[Carole]

Thanks Fay.

I don't see any problems on this image regarding the issues I had the other night with the CCD cameras, so I think this confirms that the problem is with the cameras and not the Newtonian itself.  Also am pleased to see the noise levels are better with this set up than with the DSLR and F7.5 refractors. 

Carole

[JohnP]

Looks good from Bromley Carole - also got another feint fuzzie down the bottom right hand corner... Good result will be even better once you sort out the spacings.. - John

[Carole]

There is nothing I can do about spacings John, as coma corrector plus DSLR normal distance from sensor comes to 55mm which is the exact ideal distance (but I will double check up on that).  But the coma corrector thread won't fit the DSLR T piece so I need to add the 1mm (spacing) thread adapter to make them join up.

Also any further distance and I can't get focus, and any further inwards is impossible as it is the furthest inwards the focusser will go, so I am stuck.

Going to double check all the figures to make sure though (for other cameras).

Carole

[RobertM]

That's a good attempt Carole though I agree with John that something's not quite right.  Have you checked collimation is spot on ?  Also is this the SW coma corrector or Baader - don't forget the SW CC is also a slight reducer too (0.9) so the telescope would have been operating at f/4.5 and 900mm focal length.

Fay, Carole's 200P is about the same focal length as your SW120...

Robert

[Fay]

oh ok Robert

[Carole]

Hi Robert,

Well I must confess I didn't check the collimation from the previous time I used it (a few days ago) as the scope hasn't been moved since.  But it was spot on then and a defocussed star looked fine.  But although the guide graph was good I think the guiding wasn't spot on, I am wondering whether I may have to adjust some settings in PHD now I have a different scope and am using a finder guider, but not quite sure what to do.  Therefore I did a little bit of jiggery pokery in photoshop to try to round the stars up, maybe this is confusing the issue.

I think it's a Skywatcher Coma corrector Robert, doesn't say on the box (got it second hand) but it is a focal reducer so was imaging at F4.5.

Any thoughts on what settings I should adjust in PHD for this set up, I'm afraid I don't have a clue?

Thanks for your anticipated advice.

Carole

[RobertM]

Hi Carole,

It's best to get to the source of the issue otherwise you'll be plagued by it till you sell the scope.  Regarding PHD, I don't use it but plenty here do - may be someone else will pipe up with some suggestions.

Robert

[Carole]

Actually I've been thinking about it some more, and I am not sure the guiding is the issue here.  I think it's more to do with the stars coming out ever so slightly comet shaped and this only seems to show up when zoomed in greatly.  I'll do a crop of the unadjusted image and post that up.  I will also do the same with my previous image I did of this set up without the coma corrector for comparison.  Maybe I should post this up in a technical thread. 

The thing is, I can get stuff to work if it does what it's supposed to do, but I don't have the technical ability to diagnose or fix when things go wrong unless I get advice, or unless it's something I have come accross before, so I really am at the mercy of my peers.

Carole

[Mike]

Try and get hold of a copy of CCD Inspector as it will show up collimation issues with your kit.

[RobertM]

You can also check collimation with a Cheshire; one of the best Newtonian collimating devices in my opinion.  Lasers will only give you good collimation if its nearly there anyway.

Robert

[Carole]

You can also check collimation with a Cheshire

That's what I've got, the collimation was spot on 3 days prior and I hadn't moved it since, except I suppose slewing might have moved it.  But as I say the defocussed star was fine.

I am not sure there are collimation problems I think it is something else. 

Gonna look at the image I did prior to the coma corrector.

Watch this space.

Carole 

[Mike]

Is the nosepiece dead centre in the focuser? Maybe it is slightly off? Perhaps you need a self-centering adaptor?

[Carole]

Actually funny you should ask that Mike, but i noticed the flats were slightly lop sided.  I do have a centering adapter, but this is adding even more distance to the already slightly too big distance, plus I won't get focus.

Anyway, For analysis this is what I have done.

First image is of the bright stars in the two DSLR images I have done with the Newtonian so far.
the left crop was done without a coma corrector and the star is as stated bottom left but not right at the edge.
The right crop was done WITH a coma corrector (Black Eye galaxy), and this star was towards the bottom left corner.  the middel vertical double spikes I wondered whether that was to do with the CC and spacing.