10" f/5 dob - EP/barlow choices

[mark3d]

hi all. got a new 10" f/5 dob! it came with a 26mm meade series 4000 (gives us about 50x) - seems like a great all-round EP.

i would like to get a 2" GSO barlow to double that focal length so we have the equivalent of a 13mm (for about 100x). eye relief is a factor having family members with glasses (astigmatism). budget is about equal factor too.

we also want to get some planetary views so i am also considering getting a William Optics 6mm SPL 1.25", this would give us 211x.

so far thats about $200 - i would consider that good value for 50x, 100x, 211x.

i guess my first question is can anyone see any glaringly obvious problems with this plan?

also, how often am i going to be able to use the 6mm with the barlow, for effectively 420x ? will i be able to use it generally, or only on those nights with really good conditions? i'd be really happy with this plan if i was able to do this fairly often.

my only other need, not now but sometime in the near future, is for something longer than the 26mm.. something like a 40mm.. would that make it possible to see all of Pleaides in the EP at once?

just trying to make the most of the budget :)

thanks for reading!

[erick]

If you search, you'll see some on this site who love their higher magnifications (not mentioning any names, sab). It would be nice to have 420x in your eyepiece case. It won't be often that seeing is good enough, and you also have to remember that, at that magnification, Saturn zooms across your field of view, so you need nice smooth motion to keep returning it to the field of view.

Saturday night, I had my 6m in a Televue 3x barlow in my 12" f5. If my calculations were right, I was at 750x - Yikes! The seeing wasn't really up to it, but I was looking at the crater Plato and surrounds and later on at Saturn filling much of the field (or so it seemed) and enjoying trying to track with the dob. When that magic night of good seeing comes along, I'll be ready.

I also have the GSO 2" ED barlow. I'm no expert and not particularly fussy (yet!) - so it seems fine to me.

Going to longer focal length eyepieces - As I recall, depending on scope performance, you reach a point where the secondary and spider become visible in the eyepiece when focussed on the stars (Help me here expert people). I know that a GSO 40mm in my 8" is OK in the dark, but during daylight, the secondary and spider are clearly in the view. So you'll need to experiment with some borrowed eyepieces. What you may prefer, instead of a longer focal, is a greater apparent field of view. There are 80 deg 30mm eyepieces at the cheaper end of the market. Sure they are not great, but not completely hopeless. Maybe try one of those?

[rmcpb]

If your budget is a limiting factor, whose isn't I would look at lenses that would be commonly used on most nights and wait to buy the shorter lenses when the budget allows.

As you have a 26/13 (50x/100x) how about a 17/8.5 (73x/146x) which would be a good and useful lense on most nights.

Later on a 10/5 (125x/250x) would be worth a look.

Cheers

[mark3d]

thanks guys

you are right im trying to get as much range as possible. it sounds like it is desirable to have such short FL as 3mm available, but i wont get as much regular use out of it.

instead of $200 on a barlow and a short FL EP, the other practical option is $315 for a 1.25" Televue 8mm-24mm zoom. that would cover 53x - 159x. i could always later barlow the 8mm for 320x !

choosing EPs is harder than the scope itself! ;)

cheers for the help
Mark

[erick]

Now that's a big truism, unless money is no object! But then selecting the right eyepiece from several cases full of TV and Pentax and... eyepieces might be the problem! :D

[rmcpb]

I would avoid the zoom eyepieces as they tend to have narrower fields of view and are more complex.

Another midrange eyepiece and barlow will see you through most nights viewing, I tend to only use about three eyepieces most nights, then you can sit back, relax and use them. With a bit more experience at your scope you will slowly add other eyepieces as they become "necessary" and they compliment your observing style.

You do have some collimating tools don't you????

[mark3d]

thanks again Rob, i think you're right i should get something mid-range :thumbsup:

the eye relief sure makes this exercise a bit more costly than if i could just get a couple of PLOSSLs!

the meade 5000 series 16mm Super Wide Angle has 12mm eye relief that might be ok.. $219. that would fit into the budget.

going to keep looking into it and learning!

cheers
Mark

[erick]

If eyerelief is an important factor, look at the Vixen LV range. I have 10mm and 6mm and I am happy with these.

[stonewalled]

Following the experienced advice of others recently on this site I have acquired a Vixen 12mm NLV .

Unfortunately, the sky has been cloudy so only terrestrial viewing has been possible and the eye relief was fantastic.

Reasonably priced at $165+post. The twist-up eye cup is certainly different.

Im also looking forward to receiving my 4mm Burgess TMB Planetary which was also very well priced.

Happy hunting Mark!

[JethroB76]

In that price range, don't forget the Orion Stratus and Baader Hyperions - 68 degree AFOV and good eye relief, also barlow nicely

[mark3d]

i wouldnt rule out a vixen in the future..

for now those orion stratus 17mm look like just the ticket... !

cheers :)

[Gargoyle_Steve]

I've got a 13mm Baader Hyperion and a 17mm (well, actually 2 x 17's - for my binoviewer) and these ep's are the most used in my scope - a 12" dob with 1500mm focal length. I used the same 2 ep's more than any others in my 10" dob as well, that sort of fov and magnification make a sweet package for the dobs especially when you don't have the luxury of auto tracking as Eric pointed out.

I bought an 8mm Orion Stratus and even that I use maybe 1/6th as often as the 13mm. Forget the high mag stuff at present, it only works in very clean & clear conditions. My advise is NOT to spend for example 1/3 your budget on an ep that will get used only 1/10th of the time, that's bad economics. Instead spend something like 40-50% of your budget on a good 13mm or so ep, because it WILL get used 50% of the time or more!

Cheers!

[mark3d]

well im glad i posted here - i would have bought an eyepiece i could only use 10-20% of the time, as you say Steve!

finally decided on:

Baader Hyperion 17mm 1.25”
GSO 2” Barlow ED 2xthat's for the moment at least ;)

thanks again guys!

[rmcpb]

Brilliant choice, you will get a LOT of use out of that combo :)

Keep looking up......

[Gargoyle_Steve]

As Rob said that's a good package that should serve you well, great choice!
:thumbsup:
Make sure you post again later and tell us how they work out for you after they've had first light.

Steve

[mark3d]

well the eyepiece selection was just right i think - thanks again for the advice. although i was a bit disappointed at not seeing quite the detail i hoped on planets, but then i guess thats what the high power eyepieces, on those rare good nights, are for! :)

bit of a report here:

http://www.iceinspace.com.au/forum/showthread.php?p=303977#post303977

:)

[Gargoyle_Steve]

Sounds good Mark, liked your report there. Glad you had a great night of it.

I think you'll find that having your mirror better cooled, and of course having spot on collimation, will give you even more detail - but be realistic, I'm sure you know you won't visually see planetary details that match the better images posted on this forum.

Above all else - have fun with it all!