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Which scope/mount for imaging?

FLO

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FLO

FLO

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This year, I would like to try my hand at imaging and would appreciate some advice, please :D

I am an experienced photographer so favour using a regular digital SLR before moving on to a purpose-made imaging CCD.

Budget for scope, mount, filters ... whatever, is £1,000 (though I would be chuffed if I can do it for less :D)

What should I be considering?

Expect lots of questions :D

Thanks

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FLO

FLO

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That £1000 is going to have its work cut out! :D

Probably (I already have a camera) :|

Here's the first of many questions:

In photography, an f4 lens is an f4 lens. Is this also the case when astro-imaging? For example, other than a theoretical increase in resolution, is their a benefit to having a 10" f4 scope over an 8" f4?

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FLO

FLO

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If you increase the aperture but keep the focal ratio the same you get identical images (for a given exposure time) but the scale will be larger.

Are you sure?

In photography, a 200mm f4 lens has twice the mag' (and so less FOV) of a 100 f4 but the exposure times are the same...

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FLO

FLO

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I'm guessing to keep under a grand theres going to be an ED80 in your future.... :D

Perhaps, but... Will it be better to go for an 8" f4 Newt for its shorter exposure times and greater resolution - which must be good? Or, an f7.5 APO for its compact size and contrast?

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GordonCopestake

GordonCopestake

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I would say the mount is the most important thing. If you are doing long exposures (which you are) then you need to have the lowest periodic error you can get. The astrophyics mounts are the best, but obviously out of budget. If i was you i'de see about getting an EQ6 and an ED80, but research your own choice of mount. You can also budget in for a guide scope, rings and if you dont already have one a cheap laptop with a copy of guide dog on. This is just to start, it's a complex and expensive business imaging. I surgest you take a trip over to UKAI and read a few posts there and ask a few questions. Lots of folks willing to help here too!

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russ

russ

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The 8 inch LXD75 SNT with GOTO is within budget .... just!

:nono: :nono: :nono: :nono: :nono: :nono: :nono: :nono: :nono: :nono:

I like the LXD75 mount and I like the LXD75 OTA's but those two defnitely do not go together in perfect harmony. For imaging, I would say the 6" SN OTA is the absolute max the 75 could sensibly take. But the ED80 is a perfect match, they work very well together plus you have the option of focal reducing the ED80 back to f4.8.

My personal tip for a mount would be the HEQ5 Skyscan Pro. With a bit of haggling or with your contacts, you should be able to get one new for £750 or less. Scope wise there's a couple of secondhand ED80's around at the moment for £170. That leaves £80 for a filter. To start I would go with the 2" Baader Neodymium, only £49. Which leaves £30 for a T-adapter and 2" nosepiece from Scopes'n'skies.

JOB DONE!

As an alternative, there's also an avalanche of secondhand Vixen GP/GPE/GPDX's on Astro Ads at the moment. Great mount for imaging with low PE. But i think a lot of Vixen owners are switching to the HEQ5 and EQ6 for their greater load capacity with little loss in imaging capability.

Russ

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OXO

OXO

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I can see your point about resolution Steve to scope size, this is something thats been evident in my time imaging for example Lunar Imaging with a 8" f/5 reflector i could resolve cratelets with Plato using a coolpix 4500 now when i used say a 6" f7 refractor (Celestron) those cratelets were near on impossiable to image. In both instance's seeing was 8/10 and transaprentcy was the same also. There was of course other examples of this resolution change ie:Planetry and Dso imaging but Plato with it's cratelets is a good example.

Personally i would go for a 8" F/5 Reflector on Heq5 mount(Wouldnt worry about Skyscan so much unless you like GOTO). Maybe get the scope on a EQ6 and future proof yourself at least with the Mount :D

James

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russ

russ

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Heq5 mount(Wouldnt worry about Skyscan so much unless you like GOTO)

I used to think that too. But there's a lot more to the Skyscan than the GOTO. Much improved motors for a start, PEC and the option to autoguide as well. Plus the GOTO is so accurate, it will put what ever object you wish to image straight onto the CCD. This means you can image objects which are invisible visually in the scope. And you don't have to flaff around switching between eyepiece and camera. Great stuff!!!!

Although the 8" Newt on the EQ6 would be very nice. Add Sjyscan later.

Russ

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Jamie

Jamie

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Ok Steve here is my 2p's worth.

For the restricted budget of £1000 my suggestion would have to be

a new HEQ5 with the new ED80pro = £765.00 from SherwoodsEvostar-80ED-PRO-on-HEQ5-PR.jpg

and an 80mm achromat as a guide scope = £115.00Startravel-80T.jpg

You will also need a CCD guider that would be an SC1.5 version around (or get one used)

Please understand this one thing though IMHO this is an entry level imagers set up. (but it will do the job)

So far for this little lot you are still under budget but as for the new scopes and mount but i am sure with your contacts

you should be able to get a better deal than me just surfing for 5 mins.

BTW is your head spinning yet?

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MartinB

MartinB

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OK don't disagree with anything that has been said but this is my slant on things.

The mount - don't spend the money on goto. It's not that difficult finding suitable targets so spend more money on the mount.

Buy second hand.

Don't worry about investing for the future because you will always be able to sell quality gear and actually if you really get into it you might decide you want something different to an EQ6 anyway.

If you were able to be "flexible" on budget and not fussy about goto there is the wonderful Losmandy GM8 to consider. That would be a good investment. They are snapped up second hand though so may be difficult to come by. They are an order of magnitude superior to the Synta stuff with much superior periodic error. Alternatively think about a super polaris/grand polaris (SPs are older but generally thought of as being superior). There are plenty of these second hand very cheap for what they are. I got a super polaris for £150 and spent £200 on a new hand control and guide port. One of the best purchases I ever made. It has a great polar scope and now that I've tweaked the backlash and re greased it I can barely discern and periodic error. I can get 90 secs unguided with the combination of an ED80 and 0.5 F/R. With a drift align I am sure I could go much longer.

Start with unguided and low focal length. Guiding adds a whole level of extra complexity and isn't vital for brighter objects esp at lower focal lengths. Low focal lengths mean you can get away with shorter exposures and the wider FOV is more tolerant of tracking errors. The ED80 is a great scope and you can pick them up easily second hand but F7.5 isn't ideal. I use mine with a 0.5x Atik focal reducer but this only works with web cams. I know Rus has managed to use a celestron .63 FR with his although it is designed for SCTs.

I am very pleased with my super polaris, ED80, Atik 0.5 reducer and Atik 2HS. Total paid = £800 (all second hand bar the F/R )

image.jpg

Leo triplet mosaic of 2 images - note some trailing at 90 secs in the top image. Can be removed with a bit more processing

image.jpg

M101 - Arthur added his colour subs to this, my luminence - again 90 secs 55 subs

image.jpg

M51 - my first image with the setup a mixture of 60,90 and 120 sec subs. There was a small amount of trailing at 2 mins!

Hope that doesn't confuse things too much

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FLO

FLO

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BTW is your head spinning yet?

Just a bit :shaking2:

Thanks for all the responses everyone :D

Some more questions:

Periodic Error Correction - is that where the tracking goes off-course as a result of inaccuracies in the mounts gears/drives?

How practical is it to image thru light pollution?

Is it practical to use a DSLR for deep-sky imaging? (I'd like to avoid the complexity/cost of a laptop, at least for a while).

I appreciate the strenghs of a short-tube APO but I still, currently, favour a large/fast scope for it shorter exposure times and greater resolution; shorter exposures = less noise and less star-trails from tracking inaccuracies ..... I think?

Is this an overkill?

SKYWATCHER EXPLORER-250PX f4.8 with EQ6

image.jpg

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Jamie

Jamie

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Martin i totaly agree with the Losmandy statement.

My only problem with recommending something like the Losmandy is the cost

GM8 & polarscope = £1500 new

or you could hunt for one second hand at about £750 - £1000 depending on the seller and the market.

Also to update the Losmandy to goto is far too expensive.

I was under the impression that Steve's £1000 had to include everything needed to take up imaging

getting a Losmandy won't allow him to do that.

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Jamie

Jamie

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No Steve i wouldn't say it was over kill but yer gonna have problems getting the kit you need

for a grand mate.

Guide scope/filters power supplies blah blah blah.......

Though the guide scope might not be needed of the mark as Martin says short unguided exposures work

well with a DSLR

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