TV Plossls/Powermates: Poor Man's EP Set?

I thought of getting 3 TV plossls (32mm, 25mm, and 20mm) plus the 2.5x and 5x TV Powermates and using this setup exclusively as a "poor man's" set. Has anyone else done anything like this?

Got to thinking about this after reading R. F. Royce's website (premier mirror maker) where he said he only used a few plossls and barlows.

For a common 1200mm focal length (10" f/5, 8" f/6, 6" f/8) this would give 38x, 48x, 60x, 94x, 120x, 150x, 188x, 240x, 300x.

Advantages:
Optical excellence, comfortable eye relief (12.5mm UO ortho bothered me even though I don't wear glasses), good magnification coverage, much cheaper than say 5 Naglers.

Disadvantages: 50 degree field of view, awkward swapping of equipment

I look at both planets and DSO's. Undriven dob.

Any thoughts?

Mike Ratcliff

I've often thought about it, but one thing I rather dislike about it is needing both Powermates, but it can't be helped using the Plossls. The 5x will leave the mid-range with a hole, the 2.5x will leave the high end off. Swapping isn't that awkward, however, because the Powermates are not alternated for any sequence of increasing magnifications.

I've been experimenting with a 5x Powermate for very high magnifications. I have a 20mm Tele Vue Plossl, and I thought about getting the 15mm, but I remember that I used to get eyelash oil on that one regularly, and I decided instead to give the 21mm, 15mm, and 12mm RKEs a try. It sure is expensive to buy these directly from Edmund, but I wanted to see first-hand what the quality of new ones was like rather than taking my chances (and time) tracking them down used.
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Mike

Actually, I would recommend doing it a bit differently. The 32 and 25 are a bit close together, as are the 25 and 20. I generally aim for steps of about 1.4x (i.e. sqrt of 2). I would get the 32mm, something around 20-22mm (sorry, I don't have the plossl line memorized for what is avalable), and a 2x powermate. This will give 32, 22, 16, and 11. Then get an 8mm plossl for your planetary use, which will also hit 4mm for those rare nights. You can throw in a 6mm plossl too (which will cost less than the extra powermate) to have finer spacing at the high end if needed. This will give slightly more even coverage of the magnifications.

If that is too much money, I would skip the powermate, and maybe the 22mm. I find that I do almost 90% of my observing with my lowest power and my highest commonly useable power (in this case, probably the 32mm and the 8mm or 6mm, depending on your local seeing and what scope you are using). Lowest power for finding and wide field stuff (big nebulas and galaxies, or galaxy clusters). Highest power for planets, moon, globulars, planetary neb's, small galaxies. The in between ones are only used for mid-sized objects (i.e. medium sized galaxies or open clusters), of which there aren't actually that many.

Finally, would you consider a smaller set of higher quality eyepieces? I highly recommend the 24 panoptic - a great lowest power eyepiece for 1.25" focusers. The 24 Pan, plus an 8mm radian would actually make a nice set, and cost a bit less than the plossl set plus powermates you proposed above. Then you could add others later as needed (2x powermate would still fit in with these, as would intermediate eyepieces, etc.).

Hope this helps,

Jarad


Jarad

I've toyed with your solution in the past as well, but never got the 5x PM. I think it makes a lot of sense - your eyepiece focal lengths are close together, but that helps with the planetary powers...

It's those planetary powers that mess up any simple eyepiece plan, isn't it?

Although I think it's a good solution, have you used those high powers on an undriven dob? Depending on the dob, 240x-300x with only a 50 deg field might be a bit of a chore - but then getting widefield options at high powers gets expensive.

That's my babble on the topic.

For a common 1200mm focal length (10" f/5, 8" f/6, 6" f/8) this would give 38x, 48x, 60x, 94x, 120x, 150x, 188x, 240x, 300x.

I also have a 1219 fl scope. (8" f/6) I am currently debating upgrading to widefield ep's, but this is what I have used for a while and have been happy with. 24mm Panoptic. 15mm TV plossl, 11mm TV plossl, 9mm UO ortho, 2x TV barlow. I get 50x, 81x, 100x, 111x, 135x, 163x, 222x, 271x. I mainly look at open clusters and planets. Also enjoy globs and brighter nebulae. My most used powers are 50x, 135x, 163x, 222x, 271x.
Good luck,
Jason