Newbie here

For people new to astronomy who want to ask those questions that they were afraid to ask. Receive helpful answers here.
BlueOysterCult
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Newbie here

Post by BlueOysterCult »

Hello everybody.
I am a newbie, started astronomy 1 year ago and currently looking for a astrophotography scope.
Do the good bros here have any advice? Budget of about $2k, prefer small refractor.

Thanx.
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orly_andico
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Re: Newbie here

Post by orly_andico »

This has been repeated ad nauseum, but if you're looking at astrophotography, your first line item should be the mount. So is your $2K for everything, or is that just the scope budget and you have a separate budget for the mount?

Also will you be using a DSLR - and will it be APS-C, Full Frame (FX) - or will you be using a dedicated astro CCD.

General rule of thumb, 50% of the budget goes to the mount, maybe 30% on the scope, then 20% on the camera. If you will be using a DSLR then you have more flexibility around the mount and scope.

Do note that good mounts get expensive really fast, and they are also problematic to transport.
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Airconvent
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Re: Newbie here

Post by Airconvent »

Welcome to Singastro. I suggest you check out our FAQ and Beginner Articles. And a trip to the Astroscientific will allw you to see many scopes in one place. But before making a purchase, do join in any of the obs sessions being conducted by enthusiastic members here especially the Toa Payoh and Bishan park groups!
They will be able to showcase their scopes and explain the features, so you can decide which type suits you more.
Cheers :)
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antares2063
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Re: Newbie here

Post by antares2063 »

Hi welcome to the hobby that makes you wonder why Singapore is so cloudy and the light pollution (skyglow) is so bad .

As air convent mentioned...do join in some local astro sessions to have a idea of mounts and scopes for astrophotography . :)

Regards,
junwei
I miss the place where stars shine bright, to gaze upwards in awe of the sight
BlueOysterCult
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Re: Newbie here

Post by BlueOysterCult »

Thanks for the advice everyone.
Has anyone used the Takahashi Sky 90 for imaging?
How is the color in that scope?
If I do only narrowband imaging, should I be concerned about color aberrations?
Planning to use an APS-C sensor. Will there be vignetting? I am trying to avoid flats.
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orly_andico
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Re: Newbie here

Post by orly_andico »

I don't have a Sky90, but you can find lots of Sky90 images here - http://www.astrobin.com/gear/7399/takahashi-sky-90/

But isn't the Sky90 discontinued? unless you are looking for a used one. I know someone who used to do narrowband with an achromat so it certainly is possible. Make sure to refocus between filter changes. To give an idea, I used to use a WO Z70ED with a reducer, to do narrowband. That's an "ED" (not true APO) scope, the Sky90 is certainly better. So yes, it is doable.

Narrowband will require long, long exposures, which will make the mount precision requirement even higher. What mount are you planning to use for narrowband?
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MooEy
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Re: Newbie here

Post by MooEy »

There's a couple of it in one of the club, thou I have never really tried imaging with it. Don't think you will have much trouble with it on the colour correction, should still give pleasing images.

Flat frames, I don't think you can avoid that on aps-c, the focuser is after all quite small, once you add the reducer it should have some light falloff. Last time I checked, the threads at the end of the focuser is M56, which can be used with the borg 7911 adapter. If you go for the expensive tak reducer, it goes to a ca-35 thread which is m54.

As mentioned, it's going to hard to source for a new one, you may need to resort to hunting for a used one. I ordered the borg version instead, similar specs, 90mm fluorite at f/5.6. I guess it's difficult to resist a small and cute scope.

~MooEy~
BlueOysterCult
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Re: Newbie here

Post by BlueOysterCult »

The image circle is 45mm. This is much smaller than APS-C. Do I still need flats?
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cloud_cover
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Re: Newbie here

Post by cloud_cover »

APS-C has an image diagonal of about 30mm so an imaging circle of 45mm will fill it just fine.
Having said that, light flats are always useful because there will be some degree of vignetting. Even if this is mild, it will make the center of your photo look hazier than it needs to be as the stacking software tries to compensate for the edges. RCJ had a very good thread on the usefulness of flats although I can't find it now. The results were quite dramatic.
Secondly, light flats help eliminate those little dark blotches that are caused by dust on your objective or sensor. For this reason light flats should, preferably, be taken every time you change your equipment.
Don't be worried about taking light flats. They are very easy and fast to do since they only require a short exposure. Of course illuminating your front lens at a dark site is more challenging since its not polite to shine white lights :)
By the way, there's also dark flats which you take to eliminate hot pixels. This does not require the camera to be attached to the telescope but its temperature should be about the same as your shooting environment.
DON'T PANIC
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MooEy
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Re: Newbie here

Post by MooEy »

Image circle are quoted based on what is the largest sensor size that the manufacturer think the scope can support. It can be as low as 60% illumination and stars size can be as big as 20 microns, maybe more. 45mm diagonally is pretty much 35mm full frame(36mmx24mm), aps-c is much smaller.

As mention, flat frames can help take out dust, especially for slower optics. As it's relatively easy to take, i strongly recommend doing it. For smaller scopes, you can just use something like an ipad air to provide the illumination, don't really have to buy a dedicated el panel.

~MooEy~
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