Sorry - Another question from a Newbie

[quattrorings]

Hi

I have just got back into astronomy after many years and have bought a Meade LX90 10 Inch.

I would like be able to capture images particular of galaxies/DSO's.

I have been into photography for a number of years and have a Canon 5D Mark 2 (Full Frame Sensor) - I am not really interested in capturing still images just yet.

The question is can I use the video capability of the camera to capture these images in colour and run to a monitor. (effectively using it as a video camera)

Apologies if it is a stupid question, but advice welcome.

Regards

Andy

[Demonperformer]

Andy

Well certainly you can use it in standard mode, and display the image rather than save it. I have used this technique with 'outreach' evenings with local cub groups to great effect.

You could also set it to continue taking 'real time' exposures and update them on the screen, although TBH I am not really sure what you would gain by doing that for most objects.

Presumably, you could also take that to its logical conclusion, and use 'video mode'. My concerns would be

(a) the length of each exposure needs to be long enough to capture the subject - if it is taking several frames per second (which I presume it does in video mode) you will not get a lot from most objects on it.

( if it is running continuously, the chip is going to heat up and increase the amount of noise on each subsequent capture.

Unless I have completely missed the point, I would think you would do better using your camera to take (for example) a single 15 second exposure and display that on the screen rather than trying to capture a continuous stream of images.

My 2p ...

[quattrorings]

Many thanks this is a really helpful reply. I think what you are currently doing at the outreach meetings is where i want to start - just displaying the images rather than saving them.

Perhaps you could outline how tbis would be done - is it simply a case of getting the appropriate adaptor for the camera and connecting to the telescope - would you feed the image to the camera's LCD or and external monitor. Perhaps you can talk me through it ?

Would this technique work on galaxies or is that a completely different ball game ?

Thoughts appreciated.

[Demonperformer]

Equipment:

Canon body + T ring[1] + nosepiece[2] put in eyepiece holder instead of eyepiece.

USB cable from canon to laptop with larger external screen attached if required.

I use EOS Utils (the package that came with my 1000D) but there are other packages around if you prefer.

Align the scope using eyepiece first, then attach camera as above. Start on a bright star, because the focus is likely to be way different. A useful tip is to keep a record first time of which direction you moved the focus knob and by roughly how much, as this will put you in the ball park for all future occasions.

[e.g. on my 4", I know that I need to move the focusser 'out' by a turn of about 120 degrees compared to my 32mm e/p]. I then use 'liveview' to get the focus 'quite good'. Then add my Y-mask, and take short exposure pic (~5 seconds) to achieve 'perfect' focus. Remove mask and I'm ready to go. When you take an exposure, the computer will save it, but you can always set it to put them in a 'bin' folder, which you can subsequently delete. Do you use an equatorial wedge? If not (I don't), you will probably be limited to <1 min exposures. If so, you could go for much longer (depending on your LP conditions). Single 20-second subs will show all the Messier objects (not in any great detail, perhaps!). With 30 second subs, I was able to see Pluto with my 4", so it is quite a powerful technique. And if/when you decide you want to start AP, you just continue doing the same thing, but save the images and take a lot more of them.

HTH

[1] First Light Optics - T Rings

[2] Antares Antares basic 1.25" nosepiece to T-thread camera adaptor

[quattrorings]

Thanks - really useful reply. No I don't have an equatorial wedge and don't plan to get one until I have mastered the basics. I realise this limits me to exposure times of less than 1 minute.

I am particularly interested in showing some of the Messier objects - am I right in thinking that even on a CMOS chip these will appear as B&W or will they show any colour with such short exposure times ?

Thanks