Choosing the right kit

[deadactionman76]

Hi All,

I’m new(ish) to both astronomy and this forum so thought I’d say hello and pose a newbie question.

I’ve been lucky enough to borrow a Skywatcher 300P Flextube Dob on a try-before-you-buy basis and after just a few nights viewing, I’m absolutely hooked! However, since my main interest is astrophotography, I’ve come to realise that although the visuals on the 300P are great, without a motorised EQ mount I think I’ll struggle to get the photo quality I’m after.

I’ve set myself a £1k limit and have spent many hours browsing the range at First Light Optics. I finally arrived at the conclusion that the Celestron C10-N GT on the CG-5 mount is just what I’m looking for and I was all set to make a purchase. However, about 30 seconds later I became worried that such a large tube would be impractical, swing about in the wind and push the mount to its limit (there are posts here that support the idea). I then moved onto the Celestron C9.25-SGT XLT but that’s £300+ more expensive and pushes my budget higher still (it started at £500 so what the hell).

The smaller tube on the C9.25 does appeal as I worry that the C10 is just too big, but apart from their size, can anyone comment on how close they compare? I want to get something that’ll last and serve as a starting point for what I hope will be a rewarding if not expensive hobby.

For the moment, I’ll be using my Nikon DSLR but intend to upgrade once my bank balance recovers.

Following advice from Paxo and many of the helpful posts on this forum, I’ve gained more insight into astronomy and it’s equipment over the last two weeks than I gained in the previous three and a half decades.

Thank you all

[JamesF]

Imaging objects such as galaxies and nebulae is somewhat different from imaging solar system targets. Although scopes such as the C9.25 can be used for DSO imaging, it's expensive and tricky and they're really more suited to solar system work.

For DSO imaging, aperture is not so important as it might be for visual use. If you use a small aperture scope you can just expose the image for longer to compensate. That means that even an 80mm scope is quite adequate and if you look through the relevant sections of SGL you'll find plenty of stunning images taken with that aperture or smaller.

The usual recommendation here is that if you're interested in imaging, before spending money get a copy of "Making Every Photon Count" by Steve Richards (a regular poster here). It will explain a huge amount of information that it's very sensible to know before you start buying gear.

It's probably also fair to point out that even £1000 doesn't go that far when it comes to DSO imaging, though it is much easier if you're prepared to find second-hand gear and wait for the right things to come up for sale. If you know where you want to end up and have a plan for getting there though, it's much easier get everything piecemeal in a way that allows you to use what you already have at the earliest opportunity. Hence the recommendation to read Steve's book first

James

[Capricorn]

As James says astrophotography is a different area to visual and photography.

The scope you mention have a long focal length so any shake or tracking errors will be amplified by the long focal length. Those motors introduce some vibration which that long focal length will amplify.

The intention is the track with complete accuracy the movement of the stars, when in photography do you track a moving target and not only want but must have absolute accuracy with regards target movement on the sensor.

When you take a photograph you take one exposure, in this you may take 20 then stack one on the other to get any detail, then another 2 days processing the information.

I have a scope suitable for astrophotography, it cost £700 (an inexpensive one), the flattener cost £130, the camera adaptor cost £30. That is £860 for just the scope, no mount no DSLR. Without a diagonal and eyepiece I cannot use it for visual. Astrophotography is not a budget aspect. However as a comparison I was talking to a photographer the other day who was off to shoot some owls, the lens on his camera was a 600mm Nikon that I am more then 100% sure cost more then my car.

[deadactionman76]

Thanks for the advice and recommendation. I didn't mean to suggest £1k was my total budget, I meant that I needed to set a limit to buy my first setup and go from there. Looks like I need to do some more research (and reading) before making a purchase. I kinda want the best of both worlds so finding something I can use for visual and imaging maybe a better starting point. Maybe get a decent mount and then change the scope as time goes by? Regarding the smaller aperture, I had assumed, given the unavoidable tracking errors, I should be aiming to keep the exposure time to a minimum? I appreciate the exposure times are epic compared to normal photography, but shorter exposure with a bigger primary seemed to make the most sense... to me at least.

[John]

.....I appreciate the exposure times are epic compared to normal photography, but shorter exposure with a bigger primary seemed to make the most sense... to me at least....

Hi and welcome to the forum !

I can understand where you are coming from but I've read enough advice from the experienced imagers, and seen the evidence on here over the years to realize that a small aperture scope, overmounted (ie: the mount is way within it's limits), is the way to go to get started on deep sky imaging.

Much about astro imaging is sort of counterintuitive if you have a conventional photography background - it's just hard to shake off the knowledge that is useful in the non-astro field.

I'd certainly get the book recommended above before investing in anything.

[VigdisVZ]

Maybe get a decent mount and then change the scope as time goes by?

This.

I'm a beginner myself and after asking my local club about this they all recommended I shoot for a good mount before anything else. This led me to order a NEQ-6 mount (the CG5 and EQ5 mounts are good but not as stable and strong as the EQ6). I have several people i know who have the EQ-6 and recommend it, and even a swede here on SGL called Gunnar makes modification kits to them to avoid having the "bent screw" problem when polaris is high in the sky (as it is from Sweden).

And as scope I ordered cheaper Skywatcher Explorer 150PDS. This gives me enough to start with, and it's cheap enough not to loose any sleep once I upgrade. And with 750mm focal length it means I can get good shots of large bright DSO's like Andromeda and Orion Nebula. Also, the choice of this scope was encouraged by my veteran friends in the club since it's good for photography.

With this setup I should be able to take unguided shots of atleast 1 minute, and can easily add guiding equipment, laptops, etc later since the mount wont be a problem at this point.

Hope this helps a bit with your decision.

[JamesF]

Regarding aperture, there are a lot of different factors at play. There are times when more aperture would be helpful, but large aperture scopes come with their own problems, especially when you ideally want something with a fast focal ratio for DSO imaging. There are large aperture newtonian astrographs specifically intended for imaging use and when the time comes to put your money down I'm sure people with experience of them will be more than happy to give you the low-down on how well they work, what other kit you need and what compromises you might need to make. The impression I've always had however is that the learning curve for DSO imaging is fairly steep and that it pays not to be over-ambitious at the outset and that a small aperture reasonably well-corrected refractor will help to make those first steps easier.

James

James

[swamp thing]

1350290525[/url'>' post='1670326'] shorter exposure with a bigger primary seemed to make the most sense... to me at least.

Hi

I have no interest in astro imaging but I do know that photography laws aren't going to change. The exposure time is governed by the focal ratio (f stop) of a lens or telescope not the diameter of the primary lens. All lenses at f4 will require the same exposure time regardless of whether they are 4" or 20". All primary,s of the same f/ratio show the same brightness of image regardless of primary size.

this is why aperture (diameter of the primary) is of little concern when it comes to AP. The advantage of aperture is image scale.

[deadactionman76]

I've recently discovered that to get computer control out of a mount, I don't need the GoTo version as the Syntrek can hook up to an EQDIR box and the mount can be controlled via a laptop (all I'd ever do). I thought this might free up some cash, but now I've been convinced to buy the EQ6! Still lots to consider, but I'm getting there.

Thanks all