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Imaging without guide scope. Advice please :)


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Hey guys, just in need of a little.... guidance :(:)

I recently decided to take the plunge; get in to deep sky imaging and begin buying the required equipment. So far I've got my 127 Mak, 1000D and the new HEQ5, controlled with the netbook.

My question is; will I be able to get reasonable tracking without a guide scope? I'm wanting to have a go at something like M3 and I know the Mak is nothing like the ideal scope for DS imaging, but it's what I've got for now.

Should I be getting a new scope (small APO frac) next or a guide scope and cam to use with the Mak for a while?

Any advice welcome.

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Hi Paul, IANAI (I am not an imager) :(

Honestly not sure how long an exposure you could get without guided tracking, but it can be done.

I'd go with getting a small 'frac for DSO work, like the ever popular ED 80. A nice wide field and the short fL will make it less demanding on the tracking side of things.

The long fL of the Mak makes it more suited to planetary imaging with a webcam.

I'll now make (the almost obligatory) mention of Making Every Photon Count... that's if you haven't already got it :)

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Hi mate

As you say, the mak is definitely the wrong scope for the task being somewhat slow, you should however manage something on a bright target like M3.

I shot M3 last week with an f7.5 Apo and got a good result out of a total of 20 mins of data at ISO 800.

Assuming your Mak is about f9 or f10 you'll need about double that to get the same result, or the same at double the ISO setting.

Once you have your mount polar aligned and tracking, go to ISO 1600 or so on your camera and see how long an exposure you can get before the stars begin getting oval. You should get 20 or 30 seconds easily. If you can see M3 in the individual frames then you will get a result when stacked. Shoot as many frames as you can, shoot some matching dark frames by putting the cap on the front of the scope but leaving the rest of the settings the same. Go download DeepSkyStacker and stack em all... see what you get.

I'd recon you should get a pretty reasonable result.

M13 is another nice globular that is in a good position to capture at the mo too.

Good luck!!!

Ben

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I started imaging unguided and it's a good way to "break yourself in" so to speak. I could never manage much more than 45 secs/ 1 minute, but I know others have managed longer than that perhaps they had a better mount and better alignment.

However I agree with what the others say about you needing a different scope for DS imaging, the Mak will be fine for Moon and Planets. But while you are saving your pennies, you could by all means do some practising with your Mak, just don't expect anything too brilliant.

I started DS imaging with a W0 72 APO doublet F6 and it has been brilliant from an imaging point of view for the larger DS objects such as M42, M31, Rosette (an ED80 would be similar). I now own an ED120 as galaxies were too small, so as they say above you need several scopes for different purposes.

BTW have you got a T ring to fit your DSLR to either a suitable flattener (best), or a T adapter which will fit into the drawtube? Which brings me to another point. You really need a 2" drawtube for the DSLR - what has the Mak got? Looks like 1.25" from the sites I found it on.

Carole

Edited by carastro
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with the Celestron 80ED, 450d and the HEQ5, without doing drift align etc, my best was 4 minutes unguided, but more normally 2 to 3 minutes. With a Mak, I never tried unguided deep sky, although it did work on globs... it's a much better option for the moon and planets though.

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As Psychobilly says, you face a double whammy with the Mak; long FL and slow f ratio. There is no way round this.

But I presume you have camera lenses or lens for the 1000D? Why not start with those? You should be able to do longish exposures at short FLs. Trouble is, this is not the widefield season but the Milky Way is rising and then you could have a ball.

As for whether or not you should buy a small apo refractor... well yes, you should!

Olly

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Hey there. I must agree that the Mak isn't the best scope for DSO imagery.

That being said you still can, even unguided. It's then a matter of exposure length.

For my part, that's what i started with, a mak 127, and a CG5-GT mount. I kept exposure times at 30 seconds or so and stacked as many shoots as possible.

Here are the results :

M27

5004645264_418268bf32_b.jpg

M13

4884691579_ccb0d5d379_b.jpg

In the meantime, I've had my gear evolve. Still have the mak that just cant be beaten on planetary observation, and got myself a Equinox 8°ED for wide field. And got some guiding stuff I'm still need to experiment with.

Hope this helps...

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But I presume you have camera lenses or lens for the 1000D? Why not start with those? You should be able to do longish exposures at short FLs.

Olly

with a 50mm prime lens, 5 minutes unguided seems easy on the HEQ5.

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Cheers guys and gals! You've pretty much confirmed what I was thinking. That is, it's worth having a go but I shouldn't expect to be able to do exposures over a minute of two, tops. And alignment is critical.

I'll get saving for a frac, then. I love the little WO scopes so that's what I'm aiming for.

@Carole, yes the 127 Mak is 1.25" and I have the bits and bobs to fit the 1000D in the draw tube as I use the DSLR for Lunar imaging. Bernard (MA) tells me with the right adapters it can be converted to 2". But TBH I think I'll make do with what I've got and save the spending for the next scope.

One more question while I'm here..

Guide scope or off axis guiding? What are the pro's and con's?

Thank you all for your input. You've been most helpful, as usual :)

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Good point about using the DSLR on the mount. I was intending to ask about that, too. So a 50mm would be OK... good :(

philming, nice result. I'd be perfectly happy with a result like that :)

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OAG is more of a palaver and totally unnecessary at shorter FLs. It gets to be a boon with big SCTs etc. I vote for ST80 and pc based autoguider.

Personally the humble ED80 would be my choice of imaging refractor on a budget. It performs out of its skin.

Olly

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Oh yeah, forgot to ask. I understand how to take lights, darks and bias shots. Do I also need flats or anything else?

I have got Steve's book BTW, it's just I'm only a few pages in as yet. I'll get through it this easter break :)

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Paul, I don't generally take flats when using a camera lens... I've had issues with my normal flat techniques as the camera shutter speed always seems to end up tuned to the frequency of the refresh rate of my laptop screen and I end up with bars running through them. If using a scope then yes, you should take flats.

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I've used (in order of preference & quality):

Sky flats with underpants (boxers!) over the front

Sky flats with tracing paper

Laptop screen with tracing paper

Tracing paper and head torch

Ipad screen (White web page)

Hope this helps,

Mike

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Ah right, that's interesting. I've got a 50mm finder and the SPC900NC I could use. I just need the adapters. Awesome, cheers :eek:

Cheers for the list, Mike. That'll be handy :)

Edited by Revs
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Ah right, that's interesting. I've got a 50mm finder and the SPC900NC I could use. I just need the adapters. Awesome, cheers :eek:

Cheers for the list, Mike. That'll be handy :)

You're welcome - and the SPC900NC should do a great job. I really miss my Mak 127 and wish I hadn't sold it (although it was necessary so that I could get a 6" reflector for deep space objects). The 127's relative slowness and long focal length become considerable advantages for solar system imaging.

Especially on the moon - it feels like you're flying along it.

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I'll do a straight swap with the MN!? :)

Cheers for the link, themos. Bernard is my main suppliers of bits :icon_salut: I stick with him as he's really looked after me over the last year. The guy's a star.

Thanks again for the advice everyone. Much appreciated :eek:

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