GS880 Dob

[Prometheus]

Hi Guys and Gals,

Please let me apologise in advance for some very basic questions.

After much confusion about a new scope I've narrowed it to two. I'm probably leaning more to a GS 88O f5 dob from Andrews. I've seen plenty of praise for GSO equipment on this site.
I have never owned a dob, and would appreciate some advice on eyepieces. I would rather have fewer good quality pieces than more average ones.

Also is a Barlow of any use on a dob?

Is a paracorr required?

For info, the other scope I am considering is the Intes MK66, but I am a little worried about maintenance, ... plus the fact the price just went up.

Thanks for your help

Prometheus

[rmcpb (Rob)]

My view on eyepieces for unguided dobs is to get a couple of wide angle 68 degree low and mid range eyepieces (say a 30mm, and a 20mm), a ultra wide at about 12mm and a good barlow (Orion Shorty Plus). That way you don't have to keep bumping the scope quite as much.

If they are too expensive then some good plossls (Teleview or equivilant) are great as they are good to the edge of the image which effectively gives you a "wide angle" lense compared to the cheaper eyepieces. Of course you would still need the barlow to effectively double the number of eyepieces.

Another point is to not get any double ups. In the above selection the 30mm will become a 15mm, the 20mm will become a 10mm and the 12mm will become a 6mm. That way you are not spending money on "eyepieces" you will not use.

Just some thoughts.

Cheers

[Prometheus]

Thanks Rob.

Are they 2 inch or 1.25 inch eyepieces? I see you can get barlows for both sizes.
Also, reference coma, do find it a problem in your 8 inch?
No need for additional equipment eg paracorr?

Prometheus

[slice of heaven]

The Orion shorty + is 1.25". They are a good quality barlow
But if you get a 2" barlow that has a 1.25" adaptor you can use both size eps.
Have a look for another thread in this forum where I asked about the differences and benefits of 2"v 1.25" barlows/eps.
Alot of good replies to help you out

The thread is Barlow 1.25"v2"

Slice

[iceman (Mike)]

Hi there Prometheus.

You can't go wrong with the GS880, it's a good scope with good optics at a good price.

f/5 (fast) scopes though, are more taxing on eyepiece design and collimation. Collimation errors will show up more readily, and stars won't be sharp to the edge in cheaper budget eyepieces.

So the first step, is ensure that when you get your scope, you get some tools to help you collimate, and do lots of reading, and if possible, get along to some local asto clubs or observing groups (where's bomaderry?) to get some experienced guys to help you out. You need to know how to collimate if you own a newtonian.

For eyepieces, it depends on your budget. You said you'd prefer fewer good quality eyepieces, so that's a good starting point. Good quality may mean a wide FOV, or it may mean stars pinpoint to the edge. You can get either, or both, depending on how much you want to spend.

You can get quite a good widefield in the GSO SV 30mm, it's about 65deg FOV but stars won't be pinpoint all the way out. It will barlow well though, and become a very nice 15mm SV. And, it's only $70-$90. The Andrews 30mm UW is another example, with a wider FOV (82deg), but again at f/5 the outer 1/3 stars won't be pinpoint.

You can get good quality planetary/lunar eyepieces such as orthoscopics, that don't have a wide FOV, but stars are sharp to the edge and give good contrast on your selected target. They're also quite reasonably priced. Good quality plossls (such as televue or celestron ultima) could also be considered, they'll have a narrowish FOV (wider than the ortho), be sharp to the edge, and are suitable for a wide range of targets assuming you have enough variety in focal lengths for both open star fields and cluters, to galaxies and nebulas, to planetary/lunar.

When you're after a combination of both wide field and sharp to the edge, then you're looking at spending $200-$500 per eyepiece, for ranges such as Pentax XW, Televue Panoptic, Televue Radian, Televue Nagler.

You will need and want a barlow. A 2" barlow is definitely handy as they come with a 1.25" adapter and can be used on all of your eyepieces. A fairly good quality GSO 2x 2" is about $79. The next step up is the Celestron Ultima or Orion Shorty Plus, and then Televue 2x Barlow, and the premium is the Televue Powermate.

The barlow will double your eyepiece kit, so as Rob has said, select a range of focal lengths in eyepieces that won't be doubled up when you have a barlow. Eg: If you get a 17mm nagler and a 2x barlow, you don't need to buy a 9mm nagler.

You won't need a paracorr, cross it off the list.

Hope i've helped! Good luck and let us know what yuo decide! Keep asking questions if you're unsure!

[rmcpb (Rob)]

While GS barlows are good general purpose bits of kit, don't spend the money on Teleview or Pentax eyepieces and then tag them up with a GS barlow. The Orion would be the lower end of the barlows I would look at. The better a barlow the better chance of successfully doubling your eyepiece collection, even if your original eyepieces are budget ones a better barlow will not degrade the image as much.

Better to use what you have in the short term and save a bit longer for better quality optics in the long run.

Cheers

[ving (David)]

great choice of scope. I take it the astrophotography is of no importance to you then?

as for EPs, all has been answered here already. get a small range of good quality EPs and a good quality barlow. A poor quality barlow may actually degrade the view. dont be afraid to purchase second hand. most of us star gazers look after out gear very well and sell to upgrade or if a piece become obsolete for whatever reason....

shop around and you will be suprised what you will find on astromart and ebay (and here). I recently bought a 10.5mm televue plossl for about $60 in perfect condition.

[RAJAH235]

Hi Prometheus. Don't know if I've said hello yet, so Hi. Have you contacted the Shoalhaven Astronomers yet? Are you a member? If not, PM me for Jack A's details if required. They meet just near you at the Naval Base. A great bunch of people with lots of experience. They might even let you look thru 1 or 2 of their t'scopes!
Regards, L

[Prometheus]

Thanks very much for all the info I really appreciate your help.
I'll keep you posted on what I get. May be a week or two yet.


Jim