First EP Purchase

Gef_Dintsonian · #1 16-09-2006, 10:08 PM

OK, here I go. I have an 8" Bintel Dob (FL 1200mm; Ap 200mm; F/6) and the standard eyepieces (25", 15" and 9" Plossl). The Dob is called 'Dintsonian', as I managed to purchase it at firesale rates due to a couple of dints in the tube. They do not seem to affect the viewing experience. I'm not good with maths, so have ignored all of the FOV, eye relief, whatever else stuff.

I have a Telrad, and agree it is a great purchase, especially when used with Starry Night Backyard and its Telrad circles. I have no decent chair, but like the idea of putting the Dob on a milk crate (or a self-bodgied up small platform, when I get around to it) and keeping standing up, any suggestions welcome.

I like looking at the M objects that are about at whatever time of year I'm looking. I'm not that interested in the moon (too bright) and planets (too indistinct).

I generally jump from the 25mm to the 9mm Plossl pretty quickly in an effort to get 'closer', and have been frustrated with size of the image I see. I have had a suggestion that a wide field EP would be a good next step. I have a birthday coming but v. tight budget. I have seen (online at Andrews Comms) a William Optics "E-SWA09 9mm 1.25" SWA (72°)" for $89 plus postage.

1. Does anyone know about this eyepiece or its cousins?
2. Is a wide field EP a good idea? (and why?)
3. Is a wide field 9mm good for Messier hunting?
4. Should I just save longer (ie, forget about it for the forseeable future)?

A friend keeps talking about a Barlow, and some forums (fora?) I read seemed to be saying it is useful for planets.

5. Is that planet thing right?
6. Would a Barlow help me 'get closer' to the Messier objects?
7. Won't I get confused because I just got used to everything (except the Telrad view) being upside down?

I plan to call shop(s) Monday, but would appreciate some forum support in the interim.

...Geoff

astro_nutt · #2 16-09-2006, 10:50 PM

Hi Geoff...my first accessory purchase was a quality 2x barlow..(no plastic!) This will double the magnification of your current eyepieces...the 25mm=48x..with barlow 96x and the 9mm=133x..with barlow 266x..( to work out the magnification just divide the focal length by the Eyepiece size..eg F/L 1200 divided by 25 = 48x)
A good idea is to record your observations for future reference..noting weather conditions, time, location of object, EP's used and quality of image.
Cheers!

Gargoyle_Steve (Steve) · #3 17-09-2006, 01:00 AM

I'll try to address as many of your queries as I feel I can add constructive info to. I want to point out I have owned a scope for a whole 6 months now (well, almost!) so I'm a newbie too. I'll answer from my own experiences - these answers may not necessarily be right or wrong, but accurate from my point of view. I have a GSO 10" dob basically the same as yours, except wider mirror and f5 ratio.

Lifting the dob on a box, etc, is great for when you are viewing at a low elevation (I've made up my own special "height booster") but I found that when viewing standing up all the time I get sore feet very quickly, especially on cold nights. I'm probably going to re-make my "box" to about half it's current height (which is presenty a total of 350mm). However a good height adjustable viewing chair is even more worthwhile I think. I lashed out and bought one of those excellent viewing chairs as carried by Bintel, etc, for a bit under $200. Expensive yes, but in my opinion a great accessory. I have also used it to sit on while talking, eating and drinking at a barbecue, camping, etc, as well. Very comfortable!

My scope came with 25, 15, 9 and 4.5 mm eyepieces. The 4.5 I have never successfully used, I don't use the 9mm much, I love both the others - HOWEVER like you I felt I needed a wide field ep, as my stellar navigating skills are poor I needed it as much to actually find particular objects as anything. I think a wide angle 9mm ep is still going to be a little like looking through a keyhole, if you know what I mean, just a bigger keyhole. Depends on what you want to achieve. If you want increased magnification but with trying to keep the desired object in your field of view (dob = non-tracking = moving target) then the ep you mention sounds interesting. I have an Orion Strates 68 degree ep in 8mm for the same kind of thing, I quite enjoy using it.

I definitely recommend a truly wide angle eyepiece of some kind. About 3-4 months ago I purchased the Andrews Ultra Wide Angle 30mm 80 degree 2" barrel ep, normal price around $149 though mine was on special at the time. This ep provides approx 1.98 true degrees of sky in my scope. My enjoyment in observing in general, and my success in finding particular targets, immediately doubled! There is a review of this ep on this forum, I'll try to find it to paste the link in.

Some say save your money as ultimately you'll want to upgrade this to a better brand anyway. perhaps. I tend to disagree - again, I'm a newbie. Money is precious, and I could afford to buy this NOW, and be using it NOW to enjoy so many aspects of my observing so much more! Some objects simply demand a wider viewing angle to appreciate then in their full glory, or to view them properly in context with their surrounds. If you can afford other more expensive brands then please do purchase one.

Barlows .... a bit of a contentious issue for me actually. I have now purchased 2 - a Meade #140 2x bought brand new, and a Televue 2x (not the Powermate version) purchased 2nd hand on this forum. I bought them to assist with planetary viewing, specifically Saturn and Jupiter, and I find I do not use either of them. Yes, I effectively get a 2x magnified view, but I strongly dislike the "light scattering" that seems to take place, ie the image quality just falls apart. Perhaps I have never tried them under truly fabulous seeing conditions, but I've used them on pretty good skies, and I still don't like them. Many (most?) others on this forum however use barlow lenses frequently, and love them, so I am at a loss to explain my dislike of the results.

One last thing I will add ..... fairly good collimation in a reflector will give fairly good viewing, excellent collimation will result in excellent viewing. Details just appear in familiar objects that you would not have imagined were there, fainter objects that were previously invisible will appear, etc.
Buy yourself the Combination Sighting & Cheshire tube from Bintel, etc, and read lots about how to collimate your scope accurately. I also bought the Laser collimation tool (if you buy one get the "return beam" version, not the "standard") and I use it to check / fine tune as well.

Sorry to have taken up so much space - I wanted to point out a few things that as a newbie were important to me, but perhaps someone with greater experience / knowledge may not have highlighted these points.

Cheers!

Gef_Dintsonian · #4 19-09-2006, 07:25 PM

Thank-you Astro and Gargoyle. At this point I am going with a Tele Vue 1.25" Barlow - it's over my stingy budget, but I don't think I'll regret it.

...Geoff

janoskiss (Steve H) · #5 19-09-2006, 09:23 PM

I don't know about WO SWANs in the 8" f/6 Dob. I would not risk it without being able to try first. I think they are better in slower scopes.

A 13mm Hyperion or Stratus would make a nice deep sky eyepiece for the 8" Dob. The 13mm focal length is about right for revealing maximum detail on DSOs. These would be the least expensive widefields I'd consider for that scope. They go for around $200. They are just about an ideal magnification for planets too when barlowed. If that is too expensive then just stick to the Plossls for now. Nice upgrades in plossls would be the Antares Elites; you can get from Scopestuff.

Re barlowing, your 15mm in a 2x barlow would give a good medium planetary magnification. Barlowed 9mm will almost always be too much power, but for powers between barlowed 15 and 9mm you can add an extension tube between EP and barlow.

rmcpb (Rob) · #6 20-09-2006, 08:29 AM

Some thoughts:

I would not put the scope on a milk crate. The more you raise it the less stable it becomes, better in my opinion to get an observing chair.
The 25mm GS eyepiece is good value and will keep you going for quite a while in that power range.
As for upgraded mid range eyepieces I would suggest either a 13-15mm or 9-10mm. With your preferrence for DSOs I would probably stick with the 13-15mm range.
Wide angle eyepieces need to be good or acceptable to the edge and I would not buy one without first trying it in my scope.
If budget is an issue stick to plossls and improve the motions of your base so tracking is easier.
Your comment about the moon being too bright is valid BUT don't let that stop you observing Luna. Consider getting a variable polarising filter and a whole new observing experience awaits you.
You don't mention any collimation tools and if you don't have any I would suggest the long Cheshire eyepiece available from Bintel. By improving collimation your views will improve especially those of the moon and planets .
As for a barlow, I have two in my kit and use them mainly on the moon on those really good nights. Lots of pros and cons and you will work it out for yourself. I would suggest you get a good mid range eyepiece before getting a barlow.

Good luck.......