12" Meade Dob, Parcorr, best eyepieces?

[tnott]

At F5 the use of the Parracorr is not that necessary. Remember, it only corrects coma (comet-shaped stars with tails facing outside of field) not the commonly confused astigmatism (seagulls) seen in cheap widefields at faster focal ratios.

Try a Nagler with and without the coma correcter before buying one. They are not cheap!

You usually won't even see the coma unless you use a really well corrected eyepiece like a Nagler or Pentax. Coma is also usually less obvious at higher powers.

It is also also heavy so can affect balance.

I use a Paracorr in my 22 F3.6 scope but haven't bothered in either my ex-16" or 10" F5 scopes. Threshold for definately using one for me would be F4.5 and faster.


The Type 6 Naglers are really sharp and the wider field is handy when moving the scope manually. Same for the Ethos. Radians are perhaps 0.5% sharper on axis, have a longer eye-relief , but a smaller field.

Ditto about not usually going over 200-250X on most nights.

Maybe get a 13mm Nagler and a good Barlow?

[Screwdriverone (Chris)]

Hi Mark,

Firstly, because noone has mentioned it, a Pentax XF 8.5mm would suit your scope nicely and only costs $230. Great bang for your buck AND its a quality eyepiece with good eye relief and twist up eyecup. This size EP will give you around 180 magnification on your LB and is not as heavy as most of the combos shown here, not as much FOV as the Nagler's though.

Secondly, because I have an F5 12 inch scope and ALSO have the Pentax XF 8.5mm I can verify its performance on my scope which incidentally, is amazing!

Good place to start.....

Cheers

Chris

[ausastronomer (John Bambury)]

Hi,

I don't necessarily agree with some of the advice you have been given. I own a Televue Paracorr, 2 Televue Powermates, a 2" barlow and a 1.25" barlow and to be honest I don't think you need any of those things at the moment. In an F5 Telescope I consider a Paracorr a very marginal piece of equipment. I have one for my 18"/F4.5 Telescope and only use it with 4 eyepieces out of at least 10 that I have. (31mm Nagler, 20mm Pentax XW, 17mm Nagler and 14mm Pentax XW). I don't use the paracorr with any eyepiece in my 10"/F5 telescope or with any eyepiece in my friends 25"/F5 or his 20"/F5.

I think your existing eyepieces are pretty average and not suited to use in a telescope with an F5 focal ratio. Unfortunately the eyepieces supplied when you buy a telescope are usually cheaper ones which don't work well at F5. Telescope dealers will always sell you what they carry in stock. Meade dealers will sell you meade eyepieces. At present Meade don't have any eyepieces that I would want to own and use in an F5 telescope.

I would start from scratch (sell every eyepiece you have)and start building a quality eyepiece collection you can use in any telescope you have now and progress to into the future.

You could consider buying second hand to save some money,

The telescope you have is a good one and will give you a few years of great use before you feel a need to go to something bigger and better.

I would consider building an eyepiece set along the following lines.

Low power = 30mm Pentax XW or 27mm TV Panoptic
Med Power = 16mm Nagler T5 or 13mm Nagler T6
High Power = 10mm, 7mm and 5mm Pentax XW's and a 8.5mm Pentax XF

You could also add a high quality barlow at a later stage if you felt there was a need.

Unfortunately there's quite a few dollars worth of eyepieces listed above and you may want to convert over in stages to suit your budget and any financial constraints.

Cheers,
John B

[wavelandscott (Scott)]

I'm with John on this...although I tend to use my Parracor all of the time (my preference) I wouldn't encourage you to jump in with one now either because the value is incremental.

Concentrate on getting a good low, medium and high power eyepiece (collecting one at a time) and go from there.

The first one I'd get would be based on the type of viewing that you enjoy doing...

[toryglen-boy (Duncan)]

Originally Posted by Robh

Is it worth buying the Baader MPCC for visual observations in a low power eyepiece i.e. does it reduce outer perimeter coma noticeable?

Rob

Hi Rob

Yeah, its worth it. I use it on a 12" dob, and it makes quite a difference with lower power, wide field eye pieces, although the only two points i would make are.

1. its a pain in the niagras to get the spacings right, and getting used to it can be like working out a Chinese logic puzzle.

2. Its best used with really good quality eyepieces, as quite alot of the bad viewing can be caused by defects in eyepiece itself, and not really down to coma. that said, its a handy piece of kit, and with me getting into imaging, and eyeing up a 20" F4 dob, its gonna be an even handier thing to have around.

[Robh (Rob)]

Originally Posted by toryglen-boy

Hi Rob

Yeah, its worth it. I use it on a 12" dob, and it makes quite a difference with lower power, wide field eye pieces, although the only two points i would make are.

1. its a pain in the niagras to get the spacings right, and getting used to it can be like working out a Chinese logic puzzle.

2. Its best used with really good quality eyepieces, as quite alot of the bad viewing can be caused by defects in eyepiece itself, and not really down to coma. that said, its a handy piece of kit, and with me getting into imaging, and eyeing up a 20" F4 dob, its gonna be an even handier thing to have around.

Duncan,
Thanks for the advice.
Regards, Rob.

[ausastronomer (John Bambury)]

Hi Rob,

If you want a coma corrector for visual use only I would forget about the Baader MPC. It's an absolute pain in the niagras to adjust it every time you change eyepieces. The Televue tunable top paracorr is the only way to go for visual astronomy, notwithstanding its significantly higher cost and the fact that it increases the eyepiece focal length by an effective 15%. If you want it for imaging then that is a different matter. The Baader MPC was designed as a photographic tool, the Televue Paracorr as a visual astronomy tool. That all having been said, I think its a marginal thing and subjective to personal preference, with any telescope of F5 or slower.

Cheers,
John B

[Nesti (Mark)]

To all those who have offered advice,

Thanks for your comments and recommendations; clearly getting the right eyepiece set and accessories is a marriage between experience and gut instinct. One thing I have definitely picked up, is that optical correction devices are no substitute for quality of the primary components. ***note to memory - stop picking expensive hobbies!***


I certainly haven’t wasted my money on my current eyepieces; I’m buying a Dob for my father in law - who’s wanted a telescope since his concentration camp days when he was 6yo – and since his eyesight is moderate, I might just progressively give him what I’ve got. It looks like the current economic climate is forcing the top-end prices down, so it might be a good time to start.

I think I’ll get a couple of Tele Vue Naglers and look at Pentax next buy.

Thanks once again!

Cheers
Mark

[Sentinel]

Originally Posted by ausastronomer

In an F5 Telescope I consider a Paracorr a very marginal piece of equipment.

I agree completely with this. A luxury at f5, a necessity below f5.