newbie, EXTREMELY basic question...on astrophotography!

[dr.espo]

OK, although I have previous stargazing experience (with a Dobsonian) I have zero experience with astrophotography.

Please help me with a very novice question....If I connect my Canon Eos digital camera directly to the 1 1/4 eyepiece nozzle via a t-ring and t adapter, what magnification am I recording? The telescope is a Celestron Nexstar6SE...(150mm/1500focal length/f10.

As you can see, I am optically challenged! I am somewhat confused with the optical results since the eyepiece is not used and neither is the lens on the camera. So what size image can I expect?

Also, what methods are available to increase the image size since changing to a more powerful eyepiece is not an option!

Thank you in advance for your patience in advance!

Oh, one more question, what accessory will allow me to split the image so that I can have the eyepiece on at the same time the camera is mounted...

Best regards,

Mike

ps: magnification isn't as simple as using the camera zoom, is it???

[dmahon]

Assuming a Canon 1000D:

Field of view: 50.88' x 33.92'

Resolution: 0.79 "/pixel

To increase the image size, either increase the focal length of the scope (different scope, barlow), or decrease the pixel size (different camera).

http://www.12dstring.me.uk/fov.htm

Looks similar to a 12mm Nagler, which would be 125x in your scope.

I suppose you could split the light into two paths, but that would half the amount of light and you really want as much as possible.

[dr.espo]

Assuming a Canon 1000D:

Field of view: 50.88' x 33.92'

Resolution: 0.79 "/pixel

To increase the image size, either increase the focal length of the scope (different scope, barlow), or decrease the pixel size (different camera).

http://www.12dstring.me.uk/fov.htm

Looks similar to a 12mm Nagler, which would be 125x in your scope.

I suppose you could split the light into two paths, but that would half the amount of light and you really want as much as possible.

Wow, thanks for the reply...that web site you listed is an amazing resource, thanks much! The one thing I don't have is a barlow...I believe I may invest in the very near future!

Best regards,

Mike

[dmahon]

But...... using a barlow doubles your focal ratio. You want the focal ratio to be as fast (low) as possible for photography (except for the moon and planets).

[dr.espo]

Hmmm, well, that may be acceptable since I plan to start "in the neighborhood" initially.

Thanks for the heads up on the focal ratio, I hadn't considered that.

Mike

[geordieskies]

re. "what accessory will allow me to split the image" check out "radial guiders"

I'm sure I've also seen a "split eyepiece" which allows connection of camera and eyepiece and has a mirror to flip between the two. I don't remember what it's called.

Good Luck

[ronin]

Aren't you going the wrong way?

The image may be big but will be dim, especially on a 6SE with the focal ratio that it has.

This will mean long exposure times and as the mount is Alt/Az field rotation will come into it.

Since it is a DSLR that means that the image on the chip will be blurred and so unusable. Web cams operate byt getting lots of short duration images then selecting the best of whatever was captured. A DSLR relies on a long duration image so "movement" of any sort simply degrades the image.

The rules of daylight photography do not apply to astrophotography.

Have you rebalanced the scope with the DSLR on to compensate for the extra weight and the now changed centre of mass?

[Dave S]

re. "what accessory will allow me to split the image" check out "radial guiders"

I'm sure I've also seen a "split eyepiece" which allows connection of camera and eyepice and has a mirror to flip between the two. I don't remember what it's called.

Good Luck

You're thinking of these.

: Rother Valley Optics Telescopes, Binoculars & Accessories

Dave...

[geordieskies]

cheers Dave, I knew I'd seen it somewhere.

[Dave S]

No problem.

The number of times i've know of a piece of kit but can't remember what it's called.

[Uranium235]

First thing, stay well away from imaging with barlows unless youre doing planetary, on DSOs using a barlow will produce *horrible* results. In your case you need to go the other way and use a reducer (go faster), like dmahon said.... speed is the key.

Also as some point you will need to go 2" as using a dslr with a 1.25" adaptor wont let quite enough light in to cover the chip well.

[brantuk]

A flip mirror is a great idea, you can also split the light with an off-axis guider and use an ep instead of a guide camera. There's also another similar software tool called CCDCalc free to download so you don't have to rely on the internet when out in the field.

For dso's you will get better results using a focal reducer with that scope and/or a reducer/corrector. An OAG and reducer/corrector will cost around £200-£300 new but if you're lucky you'll get them for around £180-£200 s/h

(Edit - yup Uranium's advice on going 2" is sound too)

[dr.espo]

Thanks very much to all who replied...this is all extremely interesting. I think I am jumping the gun a bit but was interested in hearing your thoughts on this concept.

The more I think about it the more I think I'm going to go slowly AND simply. I am considering using a little gizmo that Orion puts out that holds a point and shoot camera to the eyepiece - the SteadyPix Delux camera mount I think they call it. This way I can start experimenting with photos of the moon and planets and get a little knowledge along the way. I'll keep you posted on my progress!

Thank you all,

Mike

[dmahon]

For the moon and planets, spend less than £10 on a webcam (SPC900 seems to be the one to go for) and download Registax (free).

[ollypenrice]

Magnificaton has really no meaning in imaging. Think instead of plate scale. (How big is the object on your chip?) For deep sky anything more than f7.5 is lilely to be a horror so, as stated above, no Barlows!!

Olly

[dr.espo]

ok, definitely no Barlows then! Now, has anyone used a Flipcam/UltraHD to record and stack? I ask because I have one of these cams and thought it would be higher quality than a web cam...

Thanks,

Mike