M35, why the errors

[Mav359]

Hi guys

Attached is my first process of M35 from last night, its made up of 82x120sec subs and has had 20 DARKs subtracted from it. I used a Canon 1000d & a 36mm Badder Hyperion in an Eyepiece Projection setup. Guiding was good, my PHD graph was good & i used nebulosity. However....

Processing aside there are obvious things wrong with it, firstly if you look closer the stars are egg shaped, this seems to be present in the subs as well so its not a result of the stacking. The second issue is the outer stars seems to suffer being fainter and slightly out of focus. I used a Bant Mask to do the focusing prior to taking the subs and happy that the focus was right.

On a seperate note i also had issues with my FLATS, i took 20 of them using the EOS utility after putting the camera into Av mode (i didn't know how to set nebulosity as Av mode was selected), the camera took them as RAW as appossed to Nebulosity taking the LIGHTS & DARKS as Fits, as a reult DSS would use them as they didn't all match, How do take FLATS using Nebulosity.

So, why do i have egg shaped stars & whats causing the effect on the outer stars? & Has anone a better method for capturing FLATS in the FITS format?

Cheers for any help

Oh and as always, any other opinions welcome

[nmoushon]

It looks to me that the egg shape as well as the dimming of the stars at the edge is just vignetting, which can be fixed by getting a field flattener. The stars in the center look a touch eggy to my eyes as well so maybe your polar alignment might have been a touch out as well.

[Shibby]

Hi Alan, the distortion towards the edges is known as coma, common to most reflectors. The wider the field, the more significant the effect will be, so with a wide-field eyepiece like this you're going to see the worst of it. There are lots of coma correctors on the market.

Have you tried prime focus? The results with eyepiece projection are always a bit undesirable (I did try it once with awful results).

[Sp@ce_d]

On a seperate note i also had issues with my FLATS, i took 20 of them using the EOS utility after putting the camera into Av mode (i didn't know how to set nebulosity as Av mode was selected), the camera took them as RAW as appossed to Nebulosity taking the LIGHTS & DARKS as Fits, as a reult DSS would use them as they didn't all match, How do take FLATS using Nebulosity.

I've just hit the same issue. I upgraded to Neb3 and thought I'd start capturing in Fits format. I've always done flats in EOS util with AV mode and at 4 o'clock this morning I wasn't going to start experimenting in Neb! There is a batch utility in Neb to convert from RAW to Fits but DSS still sees them as a different size & grey scale.

The only reason I'm not processing last nights in Neb as I usually do is I was imaging C/2009 Garrodd so wanted to use the comet stacking routine in DSS.

Not sure I'm going to bother with Fits again as the file size jumping from 9.2mb in RAW to 60.5mb (regardless of whether fits compression was enabled or not? ) left me with nearly 4gb of data WHITHOUT flats! My netbook was groaning and I lost a good 2-3 hours of fantastic clear sky having to restart everything twice due to, I suspect, the saturation of the usb bus with the larger file size !!

I'm still searching for the answer to the flats issue..

[Sp@ce_d]

Okay.. looks like you can set the camera to Av and in Neb leave the duration set at 0 and set the number of subs to capture. Hit capture series and away it goes, it just waits for the camera to be ready after download before firing the next so wait time seems to be ignored.

The Fits compression tick box doesn't seem to save in prefs.. not sure what's going on there..

[Sp@ce_d]

Something amiss here. Just shot 20 flats in Neb and DSS STILL thinks they are different sizes to the lights and darks !

lights & darks are 3888x2592

Flats are 3904x2602

[Sp@ce_d]

Ahh... ok.. a lesson learnt and I should know better upgrading my production systems before test.... (IT joke.. ) upgrading Neb and CDC on same night doh. what was I thinking..

Right.. in case anyone else does this.. problem is acquisition mode in prefs: Recon speed or quality. I did the lights & darks in speed & flats in quality... doh

That'll be why my file sizes are huge too.. should really be set to RAW anyway. Thats probably why it kept killing PHD & EQMOD... too much for the netbook to handle. I should have paid attention to my Neb2 settings...

[Russe]

I've got the same issue but recorded with sharpcap. my flats were avi's which I've changed into bmp's via PIPP. Now DSS is complaining. I never had this issue while recording as png. Now I thought, let's change the fits to png in photoshop, but it opens up three pictures when I open one file. I'm confused.

Anyone?

How to best record flats using a CCD not recognised by nebulosity?

[Gina]

I tried the Hyperion with 1100D and the results were dreadful. Since then I've always used prime focus. So I'm afraid I'm unable to advise on your setup.