Imagine stars (doubles/multiple, variables)

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Rosanella8
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Imagine stars (doubles/multiple, variables)

Postby Rosanella8 » Wed Apr 01, 2015 9:24 pm

Good evening every one :)

I'm almost knew here but not quite, as I've tried the robo'scopes some time before but couldn't image properly (and felt a little shy to ask :oops: ). So, I thought of subscribing last month and got started imaging few known galaxies (M1, M82, M31) and cluster (M45) to see what I would get. M82 turned out rather 'red', M1 was an overall 'brown' and M45 didn't quite show (I used 'galaxy', 120000 ms and RGB on all)

Tonight I feel a little adventurous and would like to try Algieba (Gamma-Leonis - double star system-- app.magn. +2.38/+3.51)and RZ Cassiopeia (eclipsing variable). I'm using the galaxy telescope/camera but I'm not too sure about the exposure and filter :oops: At the moment I've set an exposure time to 110000 ms and no filter . Will these settings work? :?

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garypoyner
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Re: Imagine stars (doubles/multiple, variables)

Postby garypoyner » Thu Apr 02, 2015 8:42 am

These exposures are way too long. Try 10000 and a V-filter for RZ Cas if you want to photometrically measure your image. You might even be better off using ClusterCam, as the field will be larger allowing for more comparison stars to be caught on frame.

You will have to experiment with gamma Leo. Start at 5000 unfiltered and see how you get on. Even 10000 might be too much. Someone who has tried this may want to comment here. For gamma Leo you will want your star image to be as small and 'tight' as possible, and this can only be achieved with a short exposure. Also the longer you expose for, you run the risk of some trailing from the drive.

The GalCam is a very sensitive CCD, and it's a common error made by many using the telescope to have too long exposures. On a good night with the C14 and GalCam, magnitude 20 can be reached with a 50 seconds unfiltered exposure.

RZ Cas is also an SD type star, so if you plan a long 'campaign' on this EB, look out for this small amplitude 'intrinsic' variation. I have to say though that your chances of getting RZ Cas returned at this time of year are slim. The field lies only 19 degrees from the pole, and experience tells me that the telescope rarely images in this area. It's also now unfavourably placed in the NW and getting lower. Think about another target for a couple of months and don't waste your money.

Good luck,
Gary

Rosanella8
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Re: Imagine stars (doubles/multiple, variables)

Postby Rosanella8 » Thu Apr 02, 2015 9:41 pm

Thank you Gary for your advise :)
I've cancelled previous request for Algieba and re-scheduled Algieba with 5000 ms (RZ Cas is not in my list so I must have forgotten to submit a request or too sleepy, last night :D , to remember to schedule RZ Cas after writing my post) .

Which variables would you suggest I could experiment with?

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garypoyner
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Re: Imagine stars (doubles/multiple, variables)

Postby garypoyner » Fri Apr 03, 2015 1:19 pm

Crikey, where do I start? I would say that most of the VS stuff done with BRT is with CV's, however if your trying this for the first time you don't really want to be looking at very faint stars at minimum or empty sky if they are too faint for even the C14. Have a look at the BAAVSS web pages (which I look after) www.britastro.org/vss/ or the AAVSO web site www.aavso.org and here you will see lots of information and lists of stars to observe. Look at the range of the stars brightness (it's amplitude), check at what brightness it is now as this will dictate your exposure, and what type of variable it is. For anything other than a CV I would use a V filter, as any red star (Mira, SR etc.) will appear at least two-three magnitudes brighter if you don't use a V filter. If it's a bright variable, or a Mira which is near it's maximum brightness, think about ClusterCam, as this will give you a larger field and more choice of comparison stars.

A really nice Mira star to follow is SS Her. It has a short period (107d) and an amplitude of 9.0-13.0. A 20000 exposure with a V filter should be OK on this. Keep with it throughout the observing season and you will get a nice plot at the end of it.

Do you own any binoculars or a telescope? Why not try a spot of visual astronomy with a variable star if your conditions allow? Much more fun than CCD's!

If you want more info. on this, drop me an e-mail off-forum and we can discuss further.

Good luck,
Gary

Rosanella8
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Re: Imagine stars (doubles/multiple, variables)

Postby Rosanella8 » Fri Apr 03, 2015 4:44 pm

Hello Gary :)

I have a couple of binoculars and a telescope; they're nothing adventurous at the moment :) only a cheap set W12x50ZCF binoculars I bought a while back and a Meade ETX-70AT that a friend has lent me so that I can get used to finding objects through a 'scope before actually buying one.

Yes, I have looked at Britastro's, AAVSO and Popastro's list of variables but I never quite know where to begin just by looking at the data (magnitude, amplitude, etc.. :? ) and give up asking myself :D 'ok...so do I need a filter here, how long should I keep exposure time for....will the image be overexposed, :? etc....?'

I'll try your suggestion. Thank you :)


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