Which $100 eyepieces for 8" Dob?

areyouabus (Pauly) · #1 03-12-2009, 01:53 AM

Hey everyone, first post here, be gentle...

I've had my 8" (f6) collapsible skywatcher dob for 2 weeks now. I have just purchased a telrad and plan to purchase a GSO laser collimator and uhc filter soon.

Now i need to upgrade from the standard 10 & 20mm plossl eyepieces and need your help to figure out what to get.
I live and use it mostly in metro Perth but will try to take it to dark skys once a month.
So far i've most enjoyed looking at planets and nebula.
Im thinking of getting a 42mm 2" GSO superview for sweeping the sky and if possible in place of using the finderscope.
Frontier Optics have a 4mm 1.25" TMB/Burgess Planetary eyepiece for $89 which is apparently a bargain, is this too high power for suburban viewing?
Im then looking at a 12mm 1.25" (is there anything that comes close/beats a Pentax XF under $200?)

Advice, recommendations are greatly appreciated, thanks

astro744 · #2 03-12-2009, 06:10 AM

Welcome!

Your telescope has a focal length of approx 1200mm so a 4mm eyepiece with give you 300x which is useful on less than 5% of nights, dark or suburban. Aim for 150-200x as a max power for planets and have a quality Barlow on hand for nights when seeing (steadiness of the air) permits greater magnification.

I'm not familiar with the 42mm but for a low power sweeper it should be fine and the low power will be quite nice. The exit pupil will be about 7mm and some may argue this is approaching the high end but it depends on your age and how much your eye can hangle. If you are under 30 the 7mm is quite OK and in any case for the purpose you are using it (finder/sweeping) the exit pupil is not critical. (Exit pupil is the diameter of the light entering your eye and is equal to focal length of eyepiece / focal ratio of telescope).

Note too low power low cost eyepieces generally all suffer from field curvature and other abberations at the edge making their useable fields only about 70% in diameter. This is where only a lot more money will buy a sharper edge of field such as a 41mm Panoptic or 31mm Nagler. Again if you are young, the eye can handle field curvature much better and re-focus quicker as needed (straining the eye though).

One may argue that having the outer 30% sharp is not necessary but if you are searching for faint galaxies it could mean the difference between seeing a galaxy or not seeing one when at the edge.

Perhaps someone with a 42mm and an 8" f6 can comment if the combination is OK. I would recommend a good quality Plossl such as the Tele Vue 32mm Plossl that will give you 1.3 degrees and when combined with your Telrad should be sufficient. Also the 32mm is 1.25" and you only need a 1.25" UHC filter too. An alternative would be the 24mm Panoptic which will give you the same true field at a higher power but a nice wide and sharp apparent field albeit at a higher cost (also 1.25"). The 24mm Pan is a very nice eyepiece.

Not sure about the Pentax but I would think the quality is high. A 12mm focal length will give you 100x which is fine for most DSO's and the 2mm exit pupil will give you very good contrast.

For the cost of the three eyepieces you mentioned I would go the 24mm Panoptic and you can always save for more later. The 24mm Panoptic is a keeper and can be used and performs well on any telescope and the views are extremely pleasing.

dannat (Daniel) · #3 03-12-2009, 08:38 AM

i agree with the pentax choice - they are very good

i personally don't like ep's under about 7mm, i find the 4-5mm ep's very uncomfortable to look thru..i advise before you buy one to try somewhere

you might also consider an ortho for planets..small fov (not such a problem on planets) but sharp - i have a 7.5mm which was cheap but gives nice crisp views

Batfink (Peter) · #4 03-12-2009, 09:50 AM

I have a 8" scope and the GSO 42mm 2" superview, and it's almost the only ep I use, I think it's great in giving those wide views, Orion nebula look great as well as being able to view the whole Pleiades cluster., I'm thinking of getting the 30mm superview plus the 26mm super plossl, then I should be set.

Peter

casstony · #5 03-12-2009, 10:27 AM

The pentax XF12mm is a 'try before you buy' eyepiece due to field curvature - the XF8.5 doesn't have that problem.

After using the 42mm as a finder, I think you should jump to between 13mm to 17mm - this gives 70x to 90x mag which is good for DSO's and almost always useable(depending on your local conditions). The 13 or 17 Hyperion/Stratus eyepieces are a cheaper but decent option.

Then you could go to an XF8.5mm (140x).

mental4astro (Alexander) · #6 03-12-2009, 12:26 PM

Hi all,

Just a couple of things on long focal length eyepieces I think that need to be kept in mind before buying or dismissing that include optical principles and the physiology of our eyes:

* In a fast scope, eg f/5 and faster, even f/6, the shape of the light cone is somewhat 'stumpy' compared to a slower scope. This means that the eyepiece will need to deal with light falling on it that will challenge its capabilities a lot more than a 'skinnier' cone. This in cheap eyepieces shows up as a distortion and blur along the outer edge of the field of view as it cannot focus the whole field at once. The faster the scope the greater the distortion.

* The wider the apparent FOV that the eyepiece provides, the greater the likely hood of distortion. Even the finest 100degree eyepieces WILL show this distortion in a fast scope. Here then it becomes necessary to use a 'coma corrector' to improve the image.

* Short focal length eyepieces show less distortion as they recieve light at a finer point from the cone than long focal length eyepieces.

* Using too long a focal length eyepiece for the focal ratio of the scope will result in lossing precious light coming out of the eyepiece. You will get a wider view, but the image will not be brighter as the 'exit pupil' will also illuminate your iris, not falling exclusively into you pupil.

Wavytone showed me a neat rule of thumb to show the maximum eyepiece focal length:

6mm X f/ratio of scope = max focal length of eyepiece

So for your 8" f/6 scope, the longest focal length would be 36mm. The 42mm Superview would 'waste' some light, but probably not too much.

I also think that the wider the FOV the better is overrated. Our eyes are only able to SEE a set amount in the one direction before we need to move our head. This for me wastes light, time and makes for more effort for our eyes. 68 degrees is the most our eyes can see. I looked through a 100degree EP in my dob, too much work. My opinion.

Then it is up to you to decide on the best balance of price vs. quality.

I own a GSO Superview 30mm. I've also tried eyepieces twice its price of the same focal length. The Superview showed a much smaller distortion than this more expensive EP! Not a bad alternative if a $300+ EP is not an option. I'm happy with it while I save my pennies to first remodel my dob and then to get a TMB Paragon 30mm, that is a good EP.

Shorter focal length eyepieces, like 5mm, here I think that the wide FOV of 60degrees + needs to be considered if using a dob. It makes a big difference. I have a Meade series 5000 5.5mm plossl. A good EP, though the amount of times I can use it due to atmospheric conditions I am comfortable with its price of $130 new from Bintel. If the TMB Planetary gives a generous FOV, it would be a good option for your scope.

But before you buy, try out different ones first.

Paddy (Patrick) · #7 03-12-2009, 04:48 PM

My suggestion is to wait. It might be worth doing a bit more observing and getting a sense of which focal lengths you use most. I would also recommend going to some star nights and looking through other people's eyepieces preferably in your scope. Then you will be able to invest in a small number of quality eyepieces with confidence. And you will have a good idea of what to expect for what price. Also, if you're not in a hurry, there are often very good eps for good prices that come up for sale on this site.

areyouabus (Pauly) · #8 03-12-2009, 07:43 PM

thanks for the quick replies, especially about the 12mm pentax xf issues... interesting. (im 30 and wear contacts by the way)
I went to astrofest last week and got to look through a few scopes and eyepieces. (tuc 47 looked great through a 16" dob) For some reason most people there loved 2" eyepieces for everything from 30mm up to 14mm. Im not keen on having that much weight when using high magnification. For that reason i think i'd need a 1.25" barlow too (but which one?)
My scope came with standard 10mm and 20mm eyepieces and while i prefer the 20mm eye relief, i usually dont use it for too long before whacking the 10mm in for a closer look. (incidentally, is there any particular reason why you would use a 42mm to look at the Orion Nebula? Its been the main nebula that i have looked at so far but mainly use the 10mm to view it)

I think i'll look at getting the 30mm 2" superview for sweeps and big galaxies now.

I would expect the 8.5mm Pentax XF ($229)to have better FOV than my 10mm so i think it would be the eyepiece i use more than anything - unless anyone thinks that there are better eyepieces for under $200 for viewing planets in particular.
Unfortunately i cant stretch to a Nagler/Panoptic. Looked at the Baaders, (the zoom for $299 at Andrews sounds interesting) but reviews i have read suggest that the Pentax are better for an 8.5-12mm size.

Unfortunately trying before i buy is pretty much impossible. BTOW is all we really have in Perth, has a very small range of eyepieces and is out of stock often.

astro744 · #9 04-12-2009, 07:10 AM

Quote:

Originally Posted by areyouabus

Unfortunately i cant stretch to a Nagler/Panoptic. Looked at the Baaders, (the zoom for $299 at Andrews sounds interesting).

Your original line-up was

42mm ($79) + 4mm ($89) + 12mm ($<200) = <$368.

The 24mm Panoptic is $359 and would get the most use and is lightweight and small which is what you are looking for. However you do only get 24mm focal length until you can save for a Barlow.

The Baader 8-24 Zoom is getting a lot of good reviews and will give you the focal length range you are after in one eyepiece.

I do not have the Baader zoom but do have the 24mm Panoptic and it is a wonderful eyepiece.

You could also consider staying with quality Plossls such as the Tele Vue range and get the 25mm ($119), 15mm ($109) & TV 2x Barlow ($139), (Total $367). This will give you 25, 15, 12.5, 7.5 plus the 20 & 10 you already have.

Another option is the Tele Vue 32mm Plossl ($139) and 8mm ($109), Total ($248). This will give you a very nice low power (38x) sweeping/finder eyepiece and a 150x (Planetary) eyepiece. Note the 8mm is a litle tight on eye relief but OK if you do not wear glasses.

The Tele Vue Plossl series would make a fine collection and will provide quality views. An alternative would be the Meade Series 4000 Plossl eyepieces which are very well priced and perform quite well.

The Plossl has a 50 degree apparent field and the Panoptic has 68 degrees.

GrahamL · #10 05-12-2009, 02:20 PM

Hi pauly

sounds like you had a great time at astrofest.

have a read of this article , the part on field stop will help you understand why you saw so many 2 " barrel eyepieces.
http://www.televue.com/engine/page.asp?ID=277
there are many exceptional eyepieces in a 1.25" format .

I have an 8.5 xf and think its a great eyepiece good eye relief
very light and great views .
@ 140 x or so in your scope you would likely get a lot of use imo
I think the xf stacks up against some other offerings well above $200
so finding something a little cheaper that compares is a bit of an ask .

good luck
graham

areyouabus (Pauly) · #11 09-12-2009, 03:30 PM

Well i've ordered the Pentax XF 8.5. Would have loved an XW10 but $420 was pushing it.
Next step is a barlow. I was looking at getting the Orion 2x Deluxe ($120) but an extra $19 for the Televue that astro744 recommended may just be worth it, especially as I plan on taking his advice and getting a Panoptic 24mm when funds allow. (or if one pops up second hand)

There wouldnt be any problems with using a televue barlow with a pentax eyepiece would there?

One last thing, what are the best deep sky objects visible before midnight at the moment?

Im having trouble finding anything above magnitude 5, especially galaxies

mental4astro (Alexander) · #12 10-12-2009, 11:53 AM

Hi areyouabus,

There is aplenty up in the sky, including plenty of galaxies for your 8" dob. I'm not just saying it, I've actually seen these faint fuzzies through an 8" dobbie from my backyard in Sydney.

Here is a short list of some goodies:

*47 Tuc- globular cluster
*Tarantula nebula- a neb. in the LMC (which happens to be a galaxy- scan around the 'spider', it is littered with clusters & nebulousity)
*NGC 253- galaxy
*The Grus quartet- 4 galaxies close together, three are easily visible
*Jupiter!

Three tips in finding some of this stuff:
1. Use binoculars if you can. They will help you see things if light pollution is a problem
2. Have a go at this gizmo you can make for yourself to help with the finder scope:
http://www.iceinspace.com.au/forum/s...ad.php?t=53378
I've been using it to great effect from my home in Sydney.
3. Be patient- these faint fuzzies donot leap out at you through the eyepiece- use averted vision to spot and observe them- it is a learnt technique where practice will make perfect.

areyouabus (Pauly) · #13 10-12-2009, 10:01 PM

thanks for the tip, will use my iphone application to get the coordinates of them and the nearest bright star and then use my telrad to zero in on them.

I just saw a couple of specials at Frontier Optics.

Denkmeier 21mm wide field eyepiece $199 P&H $13

i've seen in some old threads that this is pretty well regarded. If figure if i grab one of these, then i've got 21, 10.5, 8.5 and 4.25 covered if i also buy a televue 2x barlow. Then i just need a 30mm to finish off.

wavelandscott (Scott) · #14 11-12-2009, 01:38 AM

Quote:

Originally Posted by areyouabus

thanks for the tip, will use my iphone application to get the coordinates of them and the nearest bright star and then use my telrad to zero in on them.

I just saw a couple of specials at Frontier Optics.

Denkmeier 21mm wide field eyepiece $199 P&H $13

i've seen in some old threads that this is pretty well regarded. If figure if i grab one of these, then i've got 21, 10.5, 8.5 and 4.25 covered if i also buy a televue 2x barlow. Then i just need a 30mm to finish off.

The 21 mm Denkmeier is a nice eyepiece (as is the 14 mm)...well made and performs alongside the other top shelf gear (TV and Pentax)...will Daniel sell them one at a time?

JethroB76 (Jeff) · #15 11-12-2009, 07:55 AM

The Denks are superb EPs, also very lightweight and comfortable ER-wise to use.

srv · #16 16-02-2010, 09:10 PM

Nice to see someone else on here from Perth.

I own a 10" GSO scope with the following GSO eyepieces:
6mm, 9mm, 15mm,25mm and a 2" 32mm.

I mainly use the 25mm as the 6,9 and 15 I have trouble seeing anything much. I hate the small eye hole (relief?) on them.

I also have a GSO 2x 2" barlow which I sometimes use.
I have found that with the 2" 32mm lens , you have to move your head around a bit to get the right view.(as per what 'mentalforastro' said above)

That being said I feel the stock eyepieces are terrible and I usually pack everything up in disgust, and don't get the full benefit from my scope.

I'm kind of disappointed with my 10" dob, with the supplied eyepieces, and looking to buy something around ~100-$150.
'mentalforastro' suggested a * Meade Series 5000 Super Plossl 5.5mm, 'bout $125 in another thread.
Can anyone tell me:
- the best place to order one of these online. (remember I'm in Perth , so there are no decent telescope shops here)
- any experience with these?

I've spent ages on checking the collimation both with the collimating eyepiece and a laser and I'm fairly happy that it's setup right.

Thanks for your thoughts/ideas from one frustrated newbie.

areyouabus (Pauly) · #17 16-02-2010, 09:29 PM

Well you can see from my footer that i spent a bit more on my eyepieces. If i had any extra patience then i would have just kept an eye on the second hand eyepieces on this site. (doing this did get me the barlow and superview cheaply)
Gotta say we are very fortunate to live in Perth. Very rarely do the clouds cause problems like so many other places on the east coast.
I went to Albany a week ago and only got a few hours of viewing because of them. Must the seabreeze that blows them away for us!

dannat (Daniel) · #18 16-02-2010, 09:55 PM

Matt (srv) some ep's I would recommend are the SPL series from Willaim optics.they are about 129 or 99 from Long perng - both from Andrews Comm (check links here). the fov on these is about 55 deg. I would not spring for the meade plossl{but a ep with wider field of view)..i do have a meade SWA super wide angle 16mm, eye relief is tight (your eye has to be quite close to the glass) but the image it gives is quite good & has a nice 65 deg field of view. the meade swa is about 139 at bintel at the moment
alteratively look for a baader hperion in the used section here, you might pick one up for 140-150

mental4astro (Alexander) · #19 16-02-2010, 10:09 PM

You can get the Meade series 5000 plossl 5.5mm from Bintel:

http://bintel.com.au/

I also have the GSO SuperView 15mm, also available from Bintel and from Andrews Communications for $10 less, but taking freight into account, get both from Bintel.

The SuperView 15mm, $59 from Bintel, is a very good medium power eyepiece which will excell in your dob. It has a 68 degree FOV and really good eyerelief. The image it gives of M42 is stunning in my 10", and even better in larger scopes. 'Hickny' just got one too. The first thing he looked at was M42 through his 13.1" Odyssey dob. Quote: "ooohh, I've got goose bumps all over!".

The only other EP I use is a GSO Superview 30mm. Wonderful wide view images. Off cause, it is not of the same standard as EPs of $300+, but for less than $80, brilliant.

SRV, be patient with your 32mm. The trick with these wider FOV EPs is to let the whole of your eye do the work, not its central vision. The most light sensitive part of our eyes surrounds our central vision. 'Averted vision' is a technique where you train your eyes to see to one side of the object you are targeting. You will actually see more this way. It is a learnt technique that needs practice. Very soon it becomes second nature.

Another thing with this technique is that you need to hold your averted vision for just one moment on the same spot, then, the vail lifts!

srv · #20 17-02-2010, 11:50 AM

Thanks for the advice.
I decided that trying out an eyepiece for $59 was worth the risk,
so I have ordered one from the Bintel shop.
(The SuperView 15mm, $59 from Bintel
https://www.bintelshop.com.au/Product.aspx?ID=6871)

(I've always wondered about the wider view eyepieces anyway.)

I'll let you know how it goes.