DSLR Help

[Acamar]

Hi all,

Recently purchased a dslr (canon eos 1100d) as ive always been interested in photography, and even more so in the cosmos.

So the problem is, today i received my celestron T adaptor and T ring in order to mount the camera in my telescope (celestron astromaster 130eq) and i am having trouble on the whole focusing business.

I can take pictures of the night sky and get pretty good results with out my telescope when i have my standard lense in but when i take out the lense in order to attach it to my telescope i just can not seem to get any pictures with decent outcome.. many of which are just black

When i tried focusing on terrestrial objects like houses etc i also could not get any focus on them.

Any help is much appreciated!

[dugpatrick]

I'm not familiar with the 130eq, but it's common to have difficulty coming to focus when using a camera on a newtonian reflector. You may need to move the primary mirror closer to the secondary, or change the focuser to allow the camera to move closer to the telescope.

Many people replace stock focusers with low-profile focusers for this reason.

Down the road you may also want to use a coma corrector, and then you'll need room for it too.

In my case I was able to find a solution without changing the focuser or moving the primary mirror. I have a Celestron C8N and the focuser has screw-on attachments for 1.25" or 2" eyepieces. I was able to find a different attachment that allows focus with my camera and coma corrector. I'm assuming you have a different focuser than mine, but if you describe the situation in detail then person someone can suggest alternatives.

Doug

[Acamar]

Changing the focuser sounds like a viable option. What is a coma corrector may i ask? I am a bit of a beginner at telescopes at the moment

[dugpatrick]

Depending on the focal ratio of the primary mirror, you may notice comatic aberrations towards the edges of the view. See also: <http://en.wikipedia.org/wiki/Coma_%28optics%29>

A coma corrector will correct the aberrations. Example correctors would be Baader MPCC and Astro-Tech ATCC.

If the 130eq is f/5 then you might find the coma acceptable for viewing, but for imaging I think you'd like it corrected. It all depends on how much you want to spend on the hobby. :-)

Another thought: If you're trying to keep costs down, then you could try a webcam. On the Canon DSLR the sensor is 55mm back form the flange when fitted with a T2 ring, but with a webcam you can get the sensor much closer. A webcam would work well for video imaging of bright subjects, such as Jupiter, Saturn, and the Moon.

Doug

[LukeSkywatcher]

A barlow lens will allow you to focus with the 130.

[Acamar]

I have tried havin a two times barlow attached also and it was no help thanks for the advice doug

[Rossco72]

check that the focuser doesn't have a threaded T connection on it. Many of the synta offerings do. This allows the camera T ring to screw directly to the focuser and achieve focus.

If it doesn't (And you might have to unthread a cover) then you have to ask if it's worth spending say £100 on a lower profile focuser or just get a bigger scope with the threaded focuser for direct connection of DSLR's.

Cheers

[gdheib0430]

check that the focuser doesn't have a threaded T connection on it. Many of the synta offerings do. This allows the camera T ring to screw directly to the focuser and achieve focus.

If it doesn't (And you might have to unthread a cover) then you have to ask if it's worth spending say £100 on a lower profile focuser or just get a bigger scope with the threaded focuser for direct connection of DSLR's.

Cheers

But if it is a direct connect threaded focuser don't you again run into the focus problem again with utilizing a barlow later down the line? Mine was threaded but the threads were just a tad off but am going to just tape the mount to it until I get a better scope considering it says the low pro focusers are for the bigger reflectors and I am still just starting out and only have this little 3".

[Rossco72]

A DSLR isn't really the right tool if you are looking at using a barlow. On the whole they just arent sensitive enough and you need 4 or 9 times the exposure and they dont control noise well.

If you are using a DSLR, play to it's strengths and stick to widefield rich starfields and extended objects. With the high pixel count you can crop and zoom a little.

[gdheib0430]

Interesting...so if you are looking at a barlow and zoom on some nebula's in the future I am assuming it is best to just dish out for a nice CCD...any recommendations? And is mono better than color...I know you would have to dish out more for the filters but seems like it would give you more options.

[Rossco72]

Well yes, but...

If you have a DSLR, take some time to get some results before ploughing £££ or $$$$ into CCD, Filters, Filter Wheel etc.

If you do go down the CCD route, mono is more flexible but more time consuming. With our light pollution, narrowband filters are essential, however if you have good skies you can get stunning results from a colour CCD.

If you are flush, get something like the Atik 4000 in both mono and colour, one to shoot the Ha or OIII detail and one to take the RGB.....

However, we all need to learn to walk before we run, its easy to spend loads and achieve little. Use your DSLR and only when it is holding you back change it out.

Cheers

[gdheib0430]

Great advice. Yeah I am on point with that will continue with the dslr and my 3" for now...eventually looking at a SSD3 mono from orion with the filters and gadgets but yeah gonna learn how to do it with less before going big. Should make the transition that much more enjoyable. thanks so much for the input I have learned so much and have tons more to learn it is helping a lot hearing from the experienced.

[Gina]

I have a Celestron Astromaster 130 EQ and have done DSLR imaging with it. The prime focus is too close to the focuser to permit use of a DSLR directly, but you can get round it. I took the lens cell from a Celestron x2 Barlow and screwed it into the thread on a T-adapter (think it's a Celestron too). I also needed an adapter to connect T-adapter to camera. These are specific to the make of camera. T-adapters are standard with a 42mm x 0.75mm pitch thread and tube to fit all 1.25" focusers.

You don't use the Barlow between camera and focuser in the usual way or you move the camera even further from the prime focus. But using just the lens part and not the tube you move the prime focus further out and can achieve focus.

The Celestron 130 EQ has a spherical mirror and won't give as good results as parabolic mirror as you get spherical aberration. But it's not bad for the money. I made good of use of it as a starter scope and it showed me where improvements were needed to move onwards and upwards

[Acamar]

What i have dont is attach the lens of my 2x barlow onto the end of my celestron t-adaptor, had to use a bit of tape because it seems its just a bit too wide to screw into the end of the adaptor. Now i can get focus so im happy Just have too wait for a nice night now!

Thanks for to everyone who has posted

[gdheib0430]

What i have dont is attach the lens of my 2x barlow onto the end of my celestron t-adaptor, had to use a bit of tape because it seems its just a bit too wide to screw into the end of the adaptor. Now i can get focus so im happy Just have too wait for a nice night now!

Thanks for to everyone who has posted

Ac, that is about what I had to do as well with my el cheapo scope while I await on getting the better scopes designed for the whole imaging field...will probably just dish out for a nice mono CCD though as my goofy sony a300 isn't the best for imaging.

[g7vhj]

Just read through this thread as i am having problems with Prime focus on a celestron 130 eq and my sons olympus dslr.

a quick question if i may, Does the 2 x Barlow get attached at the top or bottom of the camera adapter tube?

It might be a silly question but one that i am not sure about.

I have the t mount and adapter fitted to the camera with a short stub that fits into the focuser, all easy so far but I had trouble focusing on the moon last night.

I understand that it is prime focus as it felt that if i had about 1 cm more movement on the focuser then focus would have been acheived.

I then fitted the 20 mm erecting eyepiece into the scope and used the camera A focal just by placing the end of the stub upto the eyepiece in the scope and all worked ok.

I don't really want to go down the a focal route and i do use a webcam with no issues, And really can't afford to be thinking of changing scope for a better set up for a while.

regards Pete.

[donniewaffle]

Guys! I had the same problem.  You need to move the primary mirror in the scope up about 3 CM.  Yes, it sounds risky, but  just be careful, all you need is a small and large screwdriver and some longer screws.  The size/amount screws you need are six M5 60mm long  and I could not find any long enough at the hardware stores so I ordered off amazon (amazon link). I also grabbed a box of assorted springs from Home Depot, but the springs aren't 100% necessary. Just stack two springs over each screw (you will see what I mean when you look at the mirror and holder).  Seriously, not hard at all and I usually suck with stuff like this.  The only thing to note is that once you move the focus in the scope so DSLR, planetary imagers will focus, you will need an eyepiece extender (i.e. I use an Orion x2 barlow with the barlow lens screwed off)  for normal viewing eyepieces.  

[LukeSkywatcher]

On 05/12/2011 at 23:07, LukeSkywatcher said:

A barlow lens will allow you to focus with the 130.

Please ignore this comment. I must have been having a ginger moment. A barlow has very little to do with cameras,t-rings and focusing.