Photographing the Stars

[Dave Smith]

Originally Posted by Don Hoey

I have just found this link http://www.astropix.com/

Huge amount of detailed info on processing in Photoshop. A lot more than a 5 minute read.

Don

Jerry Lodriguss is quite an authority on the subject. I have copies of his two e-books (A Guide to Astrophotograpy with digital SLR cameras and Photoshop for Astrophotographers) and am currently on a very steep learning curve.

Last night it was unexpectedly clear so now have an example of the power of stacking. It is not up to Alex's standard but was taken through a 200mm lens on a driven mount that was decidedly shakey and not properly polar aligned so decided that 10s was all I could manage. One is a single 10s exposure and the other is 33 stacked 10s exposures. I hope it is obvious which is which.

Next opportunity I will mount the camera on my driven telescope and should be able to cope with longer exposures.

Dave

[Don Hoey]

Originally Posted by Dave Smith

Last night it was unexpectedly clear so now have an example of the power of stacking. It is not up to Alex's standard but was taken through a 200mm lens on a driven mount that was decidedly shakey and not properly polar aligned so decided that 10s was all I could manage. One is a single 10s exposure and the other is 33 stacked 10s exposures. I hope it is obvious which is which.

Next opportunity I will mount the camera on my driven telescope and should be able to cope with longer exposures.

Dave

Excellent job Dave. Nice to see a stack with details as you have given here. If conditions with you were similar to here in Norfolk then you get extra bonus points. Decidedly windy.

Don

[Dave Smith]

Don said "Now I just have to figure out tracking as I have a 200mm lens."

Hi Don

There a few methods of tracking the stars in order to get photos. Probably the easiest is to mount the camera on top of a driven telescope. If you don't already have an astronomical telescope then this would be the most expensive option. It is still possible to track with an undriven telescope provided a way to mount a camera on the telescope can be devised and the scope has slow motion hand controlled drives. It is better, but not essential if the scope is on an equatorial mount. To keep the camera accurately pointing you would have the scope looking at any star in a southerly direction and using the hand controls keep the star centred in the eyepiece while the camera is taking the exposure.

Most astro photos that I have taken are with the camera mounted on top of a driven scope. However, the Orion Nebula photo (see earlier post) was taken using a small driven mount that only takes the camera. Again it is not a cheap option but I have chosen it because I am taking it to Australia next April and it needs to be light enough to fit in my airline baggage allowance. I wouldn't recommend it as a method in other more normal circumstances as I am sure that for the same price (~£500) a small driven scope could be purchased which of course means you can look through it at all the wonderful sights there are in the sky.

A much cheaper option is to make (or possibly buy) a barn door mount (sometimes called a scotch mount). Here are a couple of URLs where there are full details. The photos taken with them are very impressive.


http://www.tucsonastronomy.org/barndoor.html
http://www.astronomyboy.com/barndoor/

I hope that is of some help.

Dave

[Alex Paul]

Dave: You did a great job with the shots and the stack.....I am in awe that you got the shots with a 200mm lens..... I may have to give my 400 a go with my telescope mount.... The stability would be outstanding, and obviously these lenses have plenty of resolving power with great optics. I know my 100-400 has a fluorite element and it shows no false color or CA so I would love to give it a go.... Once again very nicely done.....It has been a while since I have astro imaged and my bet is you have done a better job on these than I will manage for a while until I am back in the groove...... Skies have been hazy with large batches of clouds going through, and so seeing is less than nice and of course we have a 3/4 moon right now so even with the breaks in clouds there is more light than I want to deal with..... Hopefully in the next week or so we will have clear skies..... You guys really have me itching to get at it again.....Take care.....Alex

[Dave Smith]

Alex

Thanks for your comments. I also have a 100-400 lens and am itching to give it a go. What did you use for your Orion Nebula picture? It is an amazing shot. Am I right in thinking that it is a single shot? I am deducing that from the file name which contains a number.

Dave

[Don Hoey]

Dave,

Thanks for those links.

I had heard the term but failed to find an example. My solution in post #1 works well as long as there is enough light to see the cross hairs. These are exceedingly fine in the centre and it is highlighting these in total darkness that is my current challenge. My 35 exposure example was not tracked during exposure but each frame alinged before pressing the shutter. I am going to check out scopes with illuminating reticule as probably the cheapest solution for now.

Don

[Don Hoey]

To give an idea of the view through my telescopic sight, I took a pic today. I also took a pic of this evenings moon and scaled it to fit. To ensure accurate scale I took one through the sight itself, but that image quality is poor so I downsized a larger version.

I have set this up in dusk conditions locked onto a star just above dead centre. The star was observed for 15minutes and it held true to the cross hair until it exited view to the right. I also tracked a star quite easily over a reasonable exposure time, The 501 is quite a chunky fluid head. Easy in dusk conditions, but until I can light the crosshairs, a very tricky job in total darkness.

The crosshairs are gold and my intention is to figure a way of lighting these. I have taken advantage of glancing a mini torch beam and the effect is similar to the view in the second pic. In terms of scale, Orions belt occupies nearly the full width of the scope, unlike in this image, so manual tracking is a serious option for occasional use.

Don

[Alex Paul]

Orion ED80 600mm focal length f7.6 Apo...300D IR screen modified, with Celestron CG5GT mount.... Has electronic tracking and Go To,,,, Interfaces with laptop and GPS for precise location calibration, And I use DSLR focuser which will interface with the mounts tracking electronics and the camera for precise automated tracking correction as well as focusing the image on the screen.... The mount was 650 US and the little ED80 was 500. I shoot Prime method with camera body mounted with adapter direct to the visual back on scopes focuser tube. I looked at Losmandy mounts and love the G11 and even the smaller GM8 but it is overkill with imaging with the smaller scopes and I am happy as a clam with the capabilities of the little 80..... I have several scopes...4 Refractors ranging from 80mm to 6" 2 Schmidt Cassegrains, 8" and 9.25 1 8" Dob and an 8" newt with several different mounts of different styles, and a full set of Televue Nagler Type 2's, a few widefields in 1 1/4" along with a couple of Televue Panoptics for the gazing portion of this madness My best images were with the little 80, and the Celestron mount.... It is high enough tech, high quality imaging, low enough cost, light weight enough to move around and so it has served me well as a proper imaging set up withouit going to the Bentley end of the spectrum.... We would all love nothing but Takahashi gear but I for one work for a living..... As always it is the photographers eye, technique and understanding how to get the best out of his gear that makes a great shot, not the amount of money thrown at it....... My images all end up with numbers thrown in at the save as stage as I usually save several different variations of each and rarely actually designate a name for my images.... My last M42 shot was stacked with (to the best of my recollection) 12x 1.5 minute exposures, stacked with Registax along with one dark frame for noise reduction and dark background contrast, saved and then processed using Photoshop..... I hope with all of this babbling I have answered at least something in the original question .... I have been out of it for a while so I don't recall everything as far as exact settings and or all of the details of each shot..... I should have logged everything but of course I never did and probably never will.... I have a lot of different astro imaging software programs that I have used and loved but it will take time playing again to refresh my use and techniques with them.....I hope this is some help.......Take care Dave....Alex

[Alex Paul]

Don: I love the scope idea... It is a great way to maintain good alignment.... If you can slew smoothly to keep it where it is originally set up it a winner in every way... I think as long as you can calculate your longest acceptable exposures with out trailing.... that is the key to a good clean stack... With auto aligning in Registax and I assume others, as long as the subject is approximately in the same location in each frame the auto align feature will accept or reject the stackable images and if the exposure has to be short to be clean just shoot more frames.... The fewer frames involved with the stack the easier it is to get stellar results, however without solid, smooth, and accurate tracking capabilites the longer exposures aren't possible so you use more frames to build the image..... I am sure you already know all of this but I thought it was worth mentioning again....... You guys are an inspiration and are proving that minimalism is an excellent option once the needed technique is sorted out..... Thanks Don..... I need to get my stuff outside and start getting reaquainted with everything again.... I have an injured rotator cuff at the moment and need to be careful for a while, and with the bright moon and less than clear skies I think it may be a little while before the heavy artillery is utilized......Alex

[Don Hoey]

Phew, thats some kit Alex.

US prices are nothing like here in the UK.

Stevie has read your previous posts and has reminded me to mention she is my wife. Does this mean I also have to play the role of ' sugar daddy '.
In her astro mode she tends to be a ' space hopper ' so there has been no previous need for a tracking mount. She has drooled over bigger scopes but not really suited to her style of instant set up and go.

Excluding the camera I tend to adopt a minimalist approach to lots of my photography. If I get hooked then I may buy kit. I enjoy the challenge of working with not a lot, or ancient bits of kit that most would dismiss.

I have had another play with RegiStax, and have worked out importing multiple images. Now I have to have a further play with the interface. Never too sure when program is actually doing something without watching ' task manager ' for a bit.

Don