Finally !! M42

ZeroID (Brent) · #1 09-01-2013, 08:49 AM

Not up to scratch with others on here but it's slowly coming together. Finally got PHD Guiding going, it's bloody magic ain't it ? And my new SONY A77 is in being sorted after it's dunking so back to the KM7D through the 80mm Achro, no Barlow, just a CLS filter. Tracked M42 for 64 mins last night, first clear(ish) night in weeks. Stacked in DSS with some levels and luminance adjustments then Paint Shop Pro for colours. Stars are a bit 'eggy' due to I think the optical train having a wee bit of droop and it needs more short exposures to fill in the burnt out core. The 7D is only 6 megs so it won't stand much enlargement.

I've modified the optical train and added a 2 x Barlow for the next exercise but the real object was to get PHD going finally so I am happy with the night. Guidescope is a DIY 50 mm bino objective and SPC880 with firmware upgrade.

I've also laser collimated the 10" to see if I can sort out my coma problem. It was skewed slightly so that will be up again soon to see if it is resolved.

Poita (Peter) · #2 09-01-2013, 10:00 AM

Glad to hear you have PHD guiding going, I ended up giving up on it and moving to other software, you you have better skills than me!

barx1963 (Malcolm) · #3 09-01-2013, 11:02 AM

Starting to come together Brent!
Just one comment. You mentioned laser collimating to fix coma. If you have coma in the 10" collimation will not fix it. Coma is an inherent property of parabolic mirrors.
It can only be corrected by a coma corrector, eg Televue Paracorr or Baader MPCC.

Malcolm

ZeroID (Brent) · #4 10-01-2013, 06:21 AM

> Poita, Mine fired up second attempt, failed to connect first time but a restart of the software got it going. I'm just cheapskate, didn't want to pay out big $ for a guide scope sytem and GPUSB was only $100. I have short direct connections to the PC , camera and mount, only one short USB extension and no other hardware involved so probably minimised any possible breakdown points. Very stable the whole night, about 2hrs 30 mins with a 2 secs interval setting.

> Malcolm, 'Coma' is how I described it but that is not what it is actually. Better descibed as a 'comma' problem !! Each star image is in the shape of a small delta shaped tick instead of nice and round. Collimation is my first step. I'm hoping there isn't any major build misalignment that I've messed up, focal mount out of square etc . The camera works ok through the 80mm so that is eliminated but if the optical train is skewed .... then I'm skewed as well.

I hope not. The mirrors worked ok in Skeletope I although I never did any any pix through that. Visually I can just see the problem ( my eyes are not the best unfortunately ). More tests and investigation required.

barx1963 (Malcolm) · #5 10-01-2013, 09:22 AM

Yes, in that case it sounds more like a collimation problem.
With 'coma' the stars at the centre will be nice and sharp but near the edge will develop tiny comet like tails that all point away from the centre.
If the "commas" you are seeing are consistent across the field it is more likely to be collimation.

Malcolm

ZeroID (Brent) · #6 10-01-2013, 01:30 PM

Added a support to the optical train for the 80mm to reduce droop. Hopefully I'll run that tonight with Barlow and CLS then next up the big Newt to see if my collimation has helped any. Crossed fingers for the weather to hold out.

EQ6 is now solar battery powered as well, see this thread for any details.
http://www.iceinspace.com.au/forum/s...d.php?t=101736

SkyViking (Rolf) · #7 10-01-2013, 02:15 PM

Hi Brent, it does look a bit like coma to me. Seems quite similar to what I got in my images before I used a coma corrector: http://www.pbase.com/rolfolsen/image/142166015

You can see in my case the coma was worse towards the lower left corner. That was because collimation was not spot on at that stage. When collimation is perfect the point of least distortion will lie in the centre of the frame and the stars will appear to have small comet like tails that all radiate out from the centre.
Once you get your collimation sorted you will likely find that you still see some coma, but a coma corrector is an easy fix for that. I use the Baader MPCC.

cheers,
Rolf

alistairsam · #8 10-01-2013, 03:38 PM

Hi Brent
Do you have pics of your current setup with the guidescope?
good to know that you got your guiding going, you will be able to nab those fainter targets with longer exposures.

just a few suggestions.
if this was with the 10inch newt, to me it looks like tilt in the image plane, that is your camera is not quite square to the light path as you mentioned.

When you tighten the barrel screw in your focuser, does it push your camera to one side? this is common with the GSO focusers as the clearance is about 2mm.
take 30sec exposures of orion, and rotate the camera each time. see if the elongated stars follow the rotation.

if it is collimation, stars at the edge would also have comet shape, which I can't see in yours.
second would be focus. are you using a baht mask? if not I'd strongly suggest that. its evident with the softness of m42 along with the stars on the left.
you can make a mask by printing a mask from the online tools, laminating it and then cutting it out with a stanley knife. painful, but cheap and works well.
Also use a laser along with a cheshire. the cheshire's are a lot more accurate than the lasers, especially if the laser isn't collimated.

lastly, how long were your subs and how many subs did you stack?

ZeroID (Brent) · #9 10-01-2013, 07:39 PM

Hi Rolf, Alistair. The submitted photo above is NOT from the 10" Newt. It's through the little 80mm Achro and it does have a little droop now hopefully adjusted for. It may show some coma, more testing required as below.
Doesn't look promising for the clouds tonight dammit but I want to have another go at M42 with the remodified 80mm setup before I move onto getting the 10" tested further.

SUBS were 1 min at ISO 1600, 64 frames through a CLS filter. Some light haze cloud at one point. I need to take some short subs for the core and I need to learn a LOT MORE about processing. It is only a 6 meg camera at 80mm f5 so enlargment for more detail is hardly an option. I have a Bahtinov for the 10" but not the 80mm.

The current setup is the 114\900 Newt side by side with the 80mm Achro which has the 7D camera in back. DIY Guide scope is mounted in my DIY adjustable system on the 80 mm and the right angle finder is also attached in the 80mm dovetail. I also added the RDF on one side to make it easier to get the whole system on target to begin with. I've just come in from aligning the whole lot up. The 114 newt is for visual or webcam. Nice to be able to view while the camera works and I've been checking the guiding consistency with it.

If focuser alignment proves to be the culprit on the 10" I can compensate at the mounting plate. The stars are all comma\tick shaped in one direction across the whole fov so not coma as I understand it. My bad in the description.

Can't post a pic at present, the 7D is 'bolted' to the scope and my new SONY A77 is being assessed for water damage repair\replacement. We got drenched in a downpour while out walking Boxing day.