Telescope upgrade time

[adrianelliott]

Guys,

Any idea of a good sweet spot between size and portability to go for? I love my current setup, and want to maintain the ability to track objects for visual use, but want more aperture for DSO. Take M51 for example, in my current scope it is a faint glow. While I'm not expecting to see dust lanes, i would like to be able to resolve it a bit better and maybe increase its brightness through the eyepiece. I am realistic in my expectations, and like many things i hope there is some sort of sweat spot option which will give me better views but I can throw into my car and set up easily.

I find my current setup pretty easy to transport. The worst thing about the setup is having to adjust and spread the legs of the EQ5. I guess the easiest option is just to upgrade the OTA to to an 8 inch, and stick with the EQ5 - but I'm worried that the extra 2 inches won't be that noticeable when observing...

My other option is to go for a dob, maybe a 12inch one. The scope will always be transported in two pieces, mount and scope, and will always be loaded and unloaded into my ford focus. Will I get a huge benefit from 12 inch over 8 inch as far as resolving detail in galaxies goes? I would probably also need tracking if I went the dob route...

My main viewing spots are in Surrey (Ranmore, Headley etc) so not dark sky locations by any means. I guess what I am looking for is something which is easily managed by a single driver, but will give me significantly better views of DSO than my current scope.

Thanks,

Adrian

[Bizibilder]

If you want portable, easy to set up and best views of DSO's then the big Dob will always win. You can get Dobs that will track. Fine for visual work but not much use for photography - but it would seen you are a visual astronomer.

http://www.firstlightoptics.com/dobsonians/skywatcher-skyliner-300p-flextube-goto.html at £1300 new!

[davo]

Does your EQ5 track? if so thinking get a 16" manual Dob + a webcam for your current set up for planetary

[Hzadbhat]

Go bigger!

The difference between my 8" and 10" is truly noticable.

Tested between both, at the same nebula with the same ep showed why bigger is better.

Whilst the 10" i have is fairly bulky and not the lightest piece of equiptment I own, I can transport it on my own. I've kept the box with foam inserts to make sure my toy is as safe as possible.

If you have a wagon, the mount goes in in one piece and the box fits as well. Not sure what vehicle you have, but maybe consider getting something big enough to carry whatever you want. Also, maybe consider a trailer to haul your gear.

The dob mount forces me to kneel on the ground for anything below about 30 deg. elevation. Put my mount in a trailer, and that problem is solved.

[swamp thing]

Hi Adrian

Don't think we've met. We (SGL Surrey observers) meet on Ranmore common most clear nights, so hopefully we'll see you up there at some point.

Anyway scopes:

I never observe from home (hideous LP there), so I have to transport my scopes in order to use them. I use a 10" Dob as my main scope, I feel it offers the best balance of, aperture, portability and set up. My main interests astro wise are Galaxies and diffuse nebulae, I find for these an 8" hasn't quite got enough kick. A 12" whilst obviously an improvement on the 10" also brings with it issues with its size and weight. This is why I wouldn't pick a 12" as my everyday scope. If you feel you can handle one every time you observe or, if you have another smaller scope to use the times that hauling the big un out isn't worth it, go for it.

A 16" from Ranmore common, or Headley down just isn't worth it IMO. Been there, done it. Big scopes promise much, but from locations like these, simply cannot deliver. The rewards do not merit the effort involved in getting them there. I seldom used my 16" from sites like these, preferring to drive far away from the London sky glow to dark places where it can start to stretch its legs. This is where owning a big scope pays off, as the rewards from a proper dark sky site are huge. For me the ultimate viewing experience, and what this hobby is all about, is a dark sky site and a large aperture Dob.......bliss

[adrianelliott]

Thanks guys, it looks like jumping from my 6 to a 10 or even 12 with give me the better views I'm looking. I'm going to try and take a look at the Skywatcher 10 inch solid body and 12 inch flex-tube. I think either will fit in my car, but whether or not I'll be comfortable setting the 12 inch up is another matter! Plan at the moment will be to keep the EQ setup for video astronomy and maybe some minor AP - and as davo said the tracking could be cool for capturing planets and brigher things from the back garden when I don't want to drive.

Steve - Ranmore common is a funny place! I have previous had dog walkers and a group guys join me for observing, but as yet I haven't seen others with astro equipment. Where about do you hang out? Do you park up in the car park and go trough the metal latched gate into the fields?

[Stargazer_00]

The 12" would be kinder on eyepieces compared to the 10". Worth considering.

[adrianelliott]

Thats because the 10inch is F4.7 but the 12inch is F4.9 right?

Something I am thinking about as well as the F ratio is that (if I understand it correctly), longer focal length means less actual field of view? So if I put a 30mm Aero in my current scope it gives 2.72 degrees at 25x mag. But if I put the same eyepiece in the 12inch Dob, then suddenly it only gives 1.36! This is kinda worrying because it means I will have to spend a lot to get an eyepiece which is good for finding stuff! Do people ever use focal reducers to give wider angles?

[swamp thing]

Steve - Ranmore common is a funny place! I have previous had dog walkers and a group guys join me for observing, but as yet I haven't seen others with astro equipment. Where about do you hang out? Do you park up in the car park and go trough the metal latched gate into the fields?

We tend to use the car park itself as the roads not too busy along there later on at night.

[Stargazer_00]

Thats because the 10inch is F4.7 but the 12inch is F4.9 right?

Something I am thinking about as well as the F ratio is that (if I understand it correctly), longer focal length means less actual field of view? So if I put a 30mm Aero in my current scope it gives 2.72 degrees at 25x mag. But if I put the same eyepiece in the 12inch Dob, then suddenly it only gives 1.36! This is kinda worrying because it means I will have to spend a lot to get an eyepiece which is good for finding stuff! Do people ever use focal reducers to give wider angles?

Not really an issue in my opinion. 2.72 degrees is a real luxury. Anything around 1 - 1.5 degrees is ample for finding things in my opinion. There are always wide field eyepieces that are quite affordable these days too.

Maximum FoV of a telescope is (i believe) calculated as:

(maximum field stop of eyepiece / focal length) X 57.3

This allows you to ascertain tha physical maximum true field of view a telescope can deliver. So, yes, it stands to reason that increasing focal length will decease maximum true field of view.

27mm for 1.25" / 46mm for 2" - not all eyepieces use all field stop allowance though. And to be honest not many companies list the field stop sizes of their eyepieces either - they dont really need to though as you can work out based on the stated AFOV what TFOV the eyepiece should give and as long as that value doesn't exceed the maximim potential TFOV deliverable for the scope for that eyepiece size then your eyepiece isnt expecting more than your scope can provide.

[Stargazer_00]

Just to add, you work out the true field of view delivered from your eyepiece by dividing the AFOV by the magnification. Easy sum that one. That's why widefield eyepieces are good because they deliver more TFOV at higher magnficiations. And a TON more sky at low mags.

[Naemeth]

One thing to consider is with big dobs - the slower the dob, the higher the eyepiece is off the ground. There's a reason you don't see 24" F/6 dobs, at the Zenith the eyepiece would be about 3.65m off the ground!