First attempt at a couple of brighter DSO's

[Chris]

Hi guys,

I'm Just starting out with a bit of Astrophotraphy and thought I'd give a couple of the usual suspects a go:)

M42- 4x10 and 1x15 seconds exposure (I think) at ISO 400.

Pleiades - 12x10 seconds exposure ISO 400.

Stacked in Deep Sky Stacker and tweeked in Photo Pro.

kit - Antares 80mm f/6 refracter on a RA driven EQ5 mount plus Cannon D1100 SLR.

Advice would be more than welcome, especially about getting better tracking out of my mount as I'm struggling to get 20 seconds at present (hence short subs) with reasonable polar scope allignment:)

Regards Chris.

[Shibby]

Great start Chris, you've teased out a fair bit of detail given the very short exposure times!

You should be able to get up to a couple of minutes per sub with a good polar alignment. Make sure the reticle is aligned properly on you polar scope - this is a bit gotcha! Periodic error will probably creep in on a few exposures, but you should get enough good ones to stack an image. The more the better, I aim for at least 50 subs per image now.

Once you've got that sorted, try ISO-800. You'll find it a bit noisier but you will pick up more signal and with enough subs, the noise will stack out.

[stan26]

Hi Chris, Thats a good effort considering you have only just started out in astro photography. I'm very much in the same boat with regards to the gear I'm using, an un-guided EQ3-2 and F5 refractor. My next target is M45 then I will move onto M42 once its about at a sensible time. The orion neb is alway a pleasing target to image even with the shortest of exposures.

With regard to your tracking issues the best thing you can do is get the polar alignment spot on! Using a polar scope will get you roughly in the right spot but performing a drift alignment will enable you to go for longer subs and keep more of them. I have attatched a PDF file that explains how to perform a star drift align using your DSLR. I appreciate that it can be a pain to do this everytime before imaging but you will see better results, I know I certainly have, although my mount is now sat on a pier.

Also, make sure you balance the mount correctly by positioning the weights on the weight bar. On your RA axis you want the weight slightly bias towards the side that is being pulled up on the east, so the motor is pulling the weight if that makes sense. If the weight is perfectly balanced along the RA you'll get wobbly stars because the weight will constanly be shifting sides. The motor needs to be slightly loaded up.

Hope that helps

Stan.

(P.S, I think you work with my sister Tanya....?? )

Zeroing it in[1]. Using a DSLR or CCD to Align Your Scope.pdf

[blackparticle]

Advice would be more than welcome, especially about getting better tracking out of my mount as I'm struggling to get 20 seconds at present (hence short subs) with reasonable polar scope allignment:)

A good start.

When I started out with a DSLR and was using a 400mm scope unguided on an older HEQ5, I could only manage 25-40s subs, even with reasonably good polar alignment. The closer the object to the poles, the longer the subs you can manage.

While I'm not saying people haven't achieved 1 - 2 minute unguided subs at 400 - 500mm fl, you've got to take into account the mount that was used. My NEQ6 only does 2 min unguided subs without star trailing at roughly this pixel size / focal length and I'm fairly sure it's not broken.

Anyway..

The best thing you can do with shorter subs is to take lots of them. Lots of subs will help reduce the signal to noise ratio and obviously give you more total exposure time, which is the key thing really.

What I ended up doing was push the mount and exposure time to the limit to where star trails appeared and then back the exposure time off by about 25%. There's not much point smearing the photons across cells, you might as well just take shorter subs and have them go where they should.

Have another go at Orion and see what an hour of 15s subs gives you.

Hope that helps - Alan.

[Chris]

Thanks for the encouraging comments guys, and for the advice about my tracking issues

I must admit because my reticle is not illuminated I have been ignoring the small circular orbit of Polaris and have been just trying to get Polaris as close to the centre of the polar scope as possible, so I do need to look at my reticle alligment, I will be looking into the drift method Stan (I do work with your sis, shes one of our very best student Radiographers ), at the moment objects in my field of view drift in a north easterly direction, am I right in guessing that the drift method uses this info to calculate the adjustment (I've not managed to open your link yet Stan, might be a software issue at my end, I'll use you link title too trace the original)

Good point about the RA balance weight, so if you have perfect balance then you need to move the weight down the arm a bit so there is constant tension on the gears teeth when tracking?

Like you say Shibby and Black Particle I need to use a lot more subs to increase my signal to noise ratio, then I might be able to get away with ISO 800 a bit more:)

P.s also I'm using a battery pack, so I have also recently heard that this can give poor tracking, so I'm going to try using a voltage adaptor and extension lead

once I've Implemmented the above I hope to be able to post some improved pics:)

Thanks again guys

[stan26]

Your welcome Chris.

When I was using my polar scope I used to sit a head torch so it was shining across the front of the opening to illuminate the reticle. I assume you know how to align the mount using the polar scope? Polaris needs to be centered in the little circle, But you need to set your RA dials and use some software such as "polar finder" which can be found here Free Polar Alignment Software Download Polar FinderScope by Dr. Dale Jason Version 2.04

Loads of info on the net of how to do all this.....

That PDF file should be ok, maybe you need some form of adobe reader to view it which you may not have on your pc..? Try serching on the net for drfit align with dslr, should return a few results. The basic Idea with drift align is - opposed to using an illuminated cross hair reticle you use your dslr by taking around 1min exposures of a star and whilst doing this you would slew the RA drive at max speed (i.e 8x) to the right for 30secs and then instanly change to slewing left for 30secs. This will then display the star trailed image on the camera screen which will be in a zig zag fashion if the mount is miss-aligned. You then adjust the apropriate bolts (i.e az/alt) to reduce the zig zag trailing untill you eventually get a nice straight line, then repeat the process in the other direction. As per normal drift alignment this is done using stars in the east/south or south/west or even north etc depending on whats best in your location. HTH?

As for the weight bar, yes you would slide the weight so that it loads up the drive, but on the side thats being pulled up if that makes sense?

30-40sec subs shouldn't be a problem once you have it all set up, but do expect to ditch maybe 30% + subs due to things like periodic error etc.....

Stan.

[MikeWilson]

Hi Chris,

Welcome to SGL ;-)

I just thought I'd add my 2p.. (with apologies to earlier posters, I didn't read the thread).

Firstly definitely consider running at ISO 800 and see if you can get your exposure time up to 30 seconds. That should be easily doable with your setup. Then take a LOT more subs. With such short sub length, I'd expect to see 30+ subs on these targets, at ISO 800 (or even 1600 if it's a particularly cold night).

As for darks - have you got a remote timer? Put your camera in the fridge with the lens cap on and snap away. Get 30 or so darks (at the same ISO & length) at fridge temperature. Those'll do you fine for the winter.

Hope this helps, that's a great start you've got there!

All the best,

Mike

[Chris]

Thanks Stan yeah the drift method makes perfect sense to me, I'll be giving it a go next time we get some decent seeing, I guess after a while of doing the drift method you get quicker at making the adjustments? Just out of interest, what materials did you use to build your peer? did you have issues with the ali tripod that comes with the EQ3, I think its a shame that they dont just make a down gauged EQ5 steel tripod for the EQ3 it makes sense to me

Hi Mike, thanks for the welcome I must admit I hadn't even considered using darks or flats with an SLR, I guess I just made the assumption that this was a CCD camera noise thing, I did an Astronomy degree a while a go now and I remember taking darks and flats then to subtract the noise from the CCD chip which cooling could not get rid of, I guess the same does apply to SLR's then because they are also CCD, only just put 2 and 2 together he he what sofware do you use to subtract your darks and flats from you images? I remember using something called CCDops at Uni

[stan26]

Yes, like everything with regards to setting up the kit you get quicker every time, although I still have to refer to that PDF everytime I drift align, I can't ever seem to remember what knob to adjust.

My pier was built in two stages, the first attempt was a rather ambitious approach to creating a semi-stable imaging platform. It was basicaly a 3" steel pole filled with postcrete set in a 2.5ftsq postcrete base. The top section is basicaly 3 steel tubular bars welded onto the pole with elongated holes drilled in the tops of the bars to mount the EQ3 base and allow for slight adjustment. This proved ok with keeping polar alignment and ease of setting up, but in reality it was to wobbly especialy for visual work when making focus adjustments it would take quite a few seconds to stop moving! So this called for the stage 2 modification, I drilled down into the base and concreted in 4 x 50cm M12 rods that stuck out the top, then made a 8" wood box section which I placed around the pole with the rods inside and filled it with quick setting postcrete. Its now absolutely solid! and because my decking floats over it I can walk around/past it without any vibration carried through to the scope. Ive used an old plastic 25ltr drum insulated with bubble wrap/foam and a few bags of silica gel to protect the mount/RA motor when not in use.

All materials (apart from postcrete) were what I had lying around, and a mate that can weld. Astrophotography on a very tight budget

You can see my pier here

http://stargazerslounge.com/diy-astronomer/160070-pier-mounted-eq3-2-a.html

As for the EQ3-2 tripod, its not the best, a little flex in the legs themselves and the plastic adjustment sections went brittle and started to crack.

Regards

Stan.