Need help

[Stargazer Jack]

Hi,

I am going to be using this telescope soon http://www.itelescope.net/telescope-t16 but I need some help of what filters to use. I want to image M31 and I have an hour to get some data. These are the filters I can use, Luminance, R, V, B, Ha, SII, OIII, I, and also how many should I take and for how long. Also, the one hour is of full imaging and does not include focussing, slewing, etc.

Any help would be excellent,

Jack

[milosz]

Hi Jack,

Looks like there are no RGB filters in the wheel. So for 1 hour session I would go with Luminance filter only. You will get B/W data. 1h is not too long. So the more subs you get, the better. Though the subs shouldn't be too short. I would guess 5 - 6 minutes should do fine. IMO this is very little data for the deep sky image.

Cheers,

milosz

[Stargazer Jack]

Hi milosz,

What are the BVR filters? I thought these would be like RGB but maybe not. I am new to DSO imaging so still learning about filters and stuff.

[StuartJPP]

I think B = Blue, R = Red and V = Visual (basically green), normally you would use L as well.

I could be totally wrong though, someone will be here shortly to correct me.

[Stargazer Jack]

So could I do luminance 5x120 secs at 1x1 bin, bvr 9x300 secs (3 each) at 2x2 bin? Sorry for the questions but I'm a bit confused.

[robin-m]

M31 is big, unless you use reducers will you be able to frame it at 1095 FL?

[milosz]

I thought BVR are photometric filters. Here is the spectrum graph for these:

http://sbig.impulse.net/products/ubvri_filter_curves.htm

As a comparison, Baader RGB filters:

http://www.baader-planetarium.de/sektion/s43c/download/Baader_Anti-Reflexions_LRGBC-Filter_0508_en.pdf

There is a slight difference.

Anyway, IMO 60 minutes is too short to collect data for L and colors. I would image only luminance and than process the black-white image. With only 10 minutes of luminance it will be hard to fight the noise.

milosz

[Stargazer Jack]

I had a look in CCD calculator and it looked ok but I could be wrong. After seeing some images on SGL and the filters I can use, could I make a Hubble palette of something like the rose nebula?

[milosz]

Hmm, I've never seen M31 in Hubble palette. I don't think narrow band (except Ha) works well here. Here is Ha only: http://www.beskeen.com/gallery/galaxy/m31/M31%20Andromeda%20Galaxy%20Ha%20continuum%20sub%2050pc.jpg

milosz

[milosz]

...and for narrow band you will need much longer subexposures. 10 minutes is minimum IMO.

milosz

[Stargazer Jack]

Thanks for the help Milosz. I think I with have a look at bit more because I will not image until around the 26th January so I still have some time.

[johnrt]

Hubble palette images are of emission nebula, M31 is a galaxy so won't be suitable. I would stick to the luminance filter as suggested above and process a nice mono image. I would go for as many 2/3 minute exposures as your time will allow on the scope - M31 is bright and anything longer than 2/3 minutes will blow the core out on your image.

Good luck!!

[Stargazer Jack]

Thanks for the advice