RAW image stacking ? lens info? problems with moon

[floreatfocuser]

Hi everyone, newly joined member here

I have a canon 350 with the facory lens, plus a 28-135, 80-200L and 2* converter

What lens would people suggest I add for astrophotography, I have been thinking about a canon 50 f1.4 which seems reasonable value.

Second question, when I try and take pictures of moon I always get a second image reflected on the photograph, is this a problem with my camera?

Thirdly have been trying to understand how to image stack pictures from my SLR, have managed it with modified webcam through ETX125 using registax, but wonder how I would do it with the raw images from my DSLR?


Any help would be much apreciated


Andy

[AstroTasmania]

Hi Andy

Photographing bright objects against a dark background often produces a second ghost image which comes off a lens or other surface, a common problem, I get them all the time with all my lenses, Nikkor & Canon. I off- centre the main image which also puts the reflection further away from the real image. I then remove the ghost in Adobe Photoshop.

Stacking images from a DSLR is perhaps best done in a program specifically designed with DSLR's in mind with large image files. I use Images Plus from Mike unsold, a brilliant program which is continuously being updated, also it can control your camera, aid in focusing etc. Check out Images Plus website. I have used it for several years. It is low cost and a set of tutorial CD's are available.

Clear skies...

[scorpius]

Hi everyone, newly joined member here

I have a canon 350 with the facory lens, plus a 28-135, 80-200L and 2* converter

What lens would people suggest I add for astrophotography, I have been thinking about a canon 50 f1.4 which seems reasonable value.
Andy
Welcome Andy to the forum.
Initially I would probably give away afocal photography because of the very problems you have experienced and go for Prime Focus, where you use the mirrors only.

With the 350D this may present a focal problem because the focal length of the camera from the body face to the sensor is 35mm add to this 35mm for a T Ring and a 2" adapter tube. I have addressed this by modifying a crayford focuser. See http://members.optusnet.com.au/~mar.dav/dls006.html for a pictorial guide and also a shot of the moon using a 350d in prime focus.

Also have a browse through the Photography sections of the forum. You will probably find many answers already there for your questions. If not ask away.

On second thoughts I assume you are using the ETX125 SC and not a dob

How long have you been interested in Astronomy Andy?

[Radar]

G'day Andy,

I don't really have any better answers than the ones mentioned, but welcome to the site mate. :thumbsupmate:

Ray

[rogerg]

The question of what lens to buy is not simple. How much can you spend on it? What is your preference in objects?

There's long and short focal lenght and there's cheap and expensive.

I'm guessing you've mentioned the 50mm F/1.4 because of it's quality and fast focal ratio. Is focal ratio an issue for your situation? If you are about to do a 5 second tracked exposure then I'd suggest not.

You have a reasonable zoom range already with the lenses you have, and being an L the 80-200 would probably give very acceptable results (haven't tried that one myself.. didn't know of an 80-200, only 70-200).

Personally I stick to zooms, so on the wide angle end would recommend the 17-40 F/4L. If you're wanting longer focal length however, then there's a lot of nice L's in the 300 - 400mm focal length range with reasonable focal ratios, at a price. 70-200 F2.8 is popular, so is the 300mm fixed.

If you're going to piggyback your camera on the EXT 125, then I'd suggest weight would be an issue, probably limiting you to wide angle lenses or up to 200mm but not F/2.8 as that is huge in comparison to the F/4.

As for stacking, I use RegiStar (not RegiStax) for my DSLR images. Image Plus might be better, I'm not sure - I tried it briefly but haven't had enough experience with it to comment.

[AstroTasmania]

Hi Rogerg,

I have a nice range of Nikkor & other lenses, some zoom, such as the Nikkor f/3.5 ED 24 to 120, f/2.8 ED 80 to 200, (cost over $2.3K) which are superb, but not as good as a single fixed focus lens of any within that range. The reason of course is that zoom lenses all have a lot of extra lenses, which all contribute to light loss and internal reflections, so I prefer a fixed focal length for best results. My standard 18 to 55 Canon & Nikkor are OK as is the 70 to 300, but when I bring out the Nikkor f1.2 85mm, it out performs any of the above, as I would expect.

All my single lenses for the Pentax 6x7 are excellent, maybe because they have to cover such a large image plane.

The best lens I ever used was a Leitz Sumar 90mm, which I used for the Southern Star Atlas, in the 1070's, that was pin sharp corner to corner with pin point stars.

I have seen a review of lenses suitable for astrophotography, I will try and find it

Clear skies...

[rogerg]

I wouldn't expect the 18 to 55 or 70 to 300 to win in any competition - both are non L series quite average lenses. I'm not familiar with Nikon's range and so don't intend to compare them.

Andy hasn't said anything about budget or quality expectations. For the average astro photographer I think it's a shame to compromise to a fixed focal length when zooms provide such acceptable quality and huge flexibility and enjoyment.

Image quality of Zoom vs Fixed is a debate that will go on as long as Nikon vs Canon and Mac vs PC, so not one I'm going to enter in to.

I think to answer Andy's question is very hard ("What lens would people suggest I add for astrophotography") as there's lost of ifs and buts - you can use just about any lens for astrophotography but it depends what objects you want to shoot, what your quality expectations are, what it's being mounted on, and much much more. There is no one or even 3 recommendations overall, everyone has their own experiences and hence preferences.

Personally I'd stick to my zooms as I said, 17-40L & 70-200L, and I wouldn't change what I have if I were to start a fresh.

Good luck Andy, trial and error :thumbsupmate:

[AstroTasmania]

Hi Andy

You might find this of interest to you.

There are several well-known and very knowledgeable astrophotographers who have published books, articles and CD's on the choice of cameras & lenses for astro photography, among them is Jerry Lodriguss, who has written a superb book on the topic:

Want to learn more about digital astrophotography?

A Guide to Astrophotography with Digital SLR Cameras.

The book explains how digital cameras work and everything you need to know about how to take astrophotos with them. It also tells you how to process the images after you have shot them, with step-by-step directions that will produce beautiful results. The book on CD-ROM also includes more than 100 minutes of video tutorials on image processing.

I have extracted a segment where he talks about suitable lenses, below

...In general, zoom lenses do not perform as well as fixed focal length lenses because of extra elements and compromises in the design for the ability to zoom, and are also not as fast, aperture-wise. Tests on a star field can reveal if these zooms are suitable for astrophotography. If they are used, special care must be taken to not only prevent the focus from moving during the exposure, but also to make sure the zoom control does not move under it's own weight during the exposure, a problem with single touch zoom lenses.

Here is the link to a mine of information:
http://www.astropix.com/GADC/GADC.HTM

I am sure you find out a great deal from such an experienced astrophotographer. Excellent value and it is one of several in my library.

Clear skies...

[floreatfocuser]

Sorry i havent been back to page, am a bit new to this but thought i would get an email if anyone had responded to my questions.

Hence imagine my surprise when I looked on forum today and saw all the advice.

So Thanks everyone and il try to respond to comments below:

AstroTasmania:
Thanks will have a look at image plus, have also looked at other tools, dslr focus astrosnap, and others as well so will see what imageplus looks like. Have also ordered a serial cable for camera to allow me to control expsoures from computer. Will try aligning off centre and removing ghost image with photoshop, but will admit it is still a bit of a mystery to me that program. Have bought a couple of books, one called wide field astrophotography byRobert reeves and introudction to digital astrophotgraphy again by reeves. The book you listed looks very good i must admit, think ill order it, and that site hopefully will help me with my photosop skills aswell

scorpius:
I have tried to suss out how to connect my 350d to my etx125 as prime focus but still struggling to work it out. Have looked at stuff from scopetronix but looks bulky and also problem with etx is limited size, especially space between scope and base. My back garden only allows me to see at high declination so limits attachments I can make. Have been interested in astro stuff for years. Finally bought ETX 5 years ago but stupid thing never worked properly. After trying for ages it got relegated to cupboard. Finally found weasner's site about 12 months ago and brought it back out, had a fiddle with it and now works reasonably well.

rogerg:
yeah now realise it was a bit of a niave question, my thoughts, maybe i was wrong, were that a fixed lens would give me better images, and the fast lens would allow more scope for guiding discrepancies or more options for fixed exposures. I have just fnished building a camera piggyback mount for my ETX from a garden pressure sprayer, and agree that weight will be an issue formy ETX,although I have had a good look at beefing up the clutches as much as I can. Also I am stillstruggling to sort out polar alignment with my scope, especially here in southern hemisphere. I will look at 17-40L see what size it is. I would like to use my scoep as a guide and try and get some wide angle piccies of constellations/milky way, but also will try other stuff with 70-20 ( yes sorry not 80) and maybe extender.Depends on how welL i get my guiding working. Couldn't work out if registax will stack RAw's or do you convert them to tiffs first?


Anyway thanks again, have attached my tripod picture of Mcnaught, any suggestions with regard to proessing it to get rid of the rather bad graining from a high Iso??

Andy

[rogerg]

Andy, good to see you back, these forum things do take a little figuring out at first.

Regarding stacking - yes, I convert to TIF files first. I believe that is what a large proportion of people in our situation do. A few use other programs to process the images as RAW.

Regarding your image - stacking is about the best way to remove the noise. Did you think to shoot several shots right after each other? If so you can stack those images and dramatically improve the overall quality. Otherwise, there are programs out there that amateur astronomers use for removing noise. I can't think of them right now - perhaps someone else might know? I sometimes use things like a median filter in PhotoShop, but there are smarter programs for the job.

[AstroTasmania]

Stacking with freeware programs such as RegiStax is always a good way to go if you have a few images taken close enough to avoid too much movement. The next option is a program called Noiseware, it is available as a freeware or with more features for a small dollar amount, also available as a Plugin for Photoshop.

There are several others, some of which I use and can't bring to mind their names this early in the morning. A Google search for noise reduction under image processing with turn up a few options.

I use Noiseware, both as a stand alone on one PC and as a Plugin on another.

Clear skies...

[scorpius]

Sorry i havent been back to page, am a bit new to this but thought i would get an email if anyone had responded to my questions.


Andy

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