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Posts Made By: Jackie Pritchard

September 20, 2007 05:48 PM Forum: Beginning Astronomy?

Astronomical eyepieces for Pentax PF-80ED?

Posted By Jackie Pritchard

I have a Pentax PF-80ED angled body scope coming. It is suppose to take any 1.25 astronomical eyepiece. Does anyone have practical experience with this scope or a similar one to tell me the do's and don'ts of buying eyepieces? Can it use barlows? Are some types of eyepieces too powerful (e.g. Pentax XW 3.5)? Will some eyepieces not focus properly because of size? I know I need a very good tripod with good head for astronomy viewing rather than cheap tripod - I have a Bogan with fluid head on the way.

This scope will primarily be used for daytime terrestrial viewing using the 20X60 zoom, but I would like to do a bit of nighttime viewing in the 90X to 105X range. I am unsure of the 4mm eyepiece that would give me 130X (525 divided by 4). Too much? I wanted the Pentax PF-100ED but settled for the 80mm because the larger scope does not come in angled body. I know it would be better for brightness.

I just see lots of eyepieces from Meade, Celestron, Vixen, Televue, etc and I need to know if I can buy and use any reasonably. Since my scope has a 20X60 zoom, I am assuming I mostly need to buy eyepieces in the 4-7 mm range for higher magnification. But would a 10mm or 12mm astronomical eyepiece give me better field of vision or some other quality that I could not get out of the zoom at the same magnification?

Since this is the beginners forum, I am assuming its OK to ask dumb questions like these...

October 25, 2007 05:08 AM Forum: Beginning Astronomy?

6" OR 8"?

Posted By Jackie Pritchard

I am a rank beginner but the advice I keep hearing is that a Dob is a great choice for a person starting out. I am thinking of the Orion 6" vrs 8". I know the 8" will gather more light and be a better overall value for just $100 more, yet weight is a great concern for me. Will I be disappointed in the 6"? If the 6" is going to give me good planetary views and reasonable stellar views, I could be happy with that. Long-winded way of asking: is the performance of the 6" so much less than the 8" that I should just resign myself to hoisting the extra weight? Or is the 6" adequate for the casual observer just wanting to see enough of the heavens to get a "Wow" feeling?

November 2, 2007 01:56 AM Forum: Beginning Astronomy?

Focal ratio

Posted By Jackie Pritchard

I understand that a lower ratio = faster and is better for astrophotography, while a higher ratio = slower and is suppose to give better contrast. How much contrast would you give up going from a 150mm Skywatcher at f/8 versus f/6 for example? I really want to get a higher aperture but lighter weight refractor - yet I don't plan on any photography, mostly just planetary viewing - so it seems weight and contrast are going in opposite directions for me. I somewhere read that it's best to get a slower than f/6 for visual observing, yet I read about faster focal telescopes that the manufacturers say are great for observing... If I stay in the 110mm -127mm range for a refractor, any advice of focal ratios acceptable? Sorry to be so long-winded.

November 18, 2007 08:13 PM Forum: Beginning Astronomy?

focal ratio redux

Posted By Jackie Pritchard

I thought I was beginning to get a handle on the focal ratio issue and then I read this "myth"/misconception from the Televue site:
Myth #3: Faster telescopes show brighter images.
This is a misconception carried over from photographic use, where the fast f/ratios do mean brighter images and shorter exposures for extended objects. Telescopes with equal apertures and equal magnifications have the same visual image brightness, regardless of the objective's f/number.

"Myth #4: Long-focal-ratio telescopes give higher-contrast images.
In general, refractors offer the potential for higher contrast because mirror coatings, by their nature, tend to scatter more light. But when comparing well-made, highly corrected refractors, there is no gain in contrast with instruments of long focal ratio.

Reflectors too, if well made and having the same size of secondary obstruction, will have the same contrast at the same magnification regardless of the f/ratio. "

Now I am again confused. It seems to be saying I can get a good fast apo/ed and get as good results (contrast-wise) as a slower focal ratio apo/ed telescope. I want a good 100mm-115mm refractor so as long as the optics are good, and my primary goal is planetary observations, this seems to say f ratio is irrelevant. Has that been a common experience? Is the ratio only important for astrophotography? Is "contrast" not the same as seeing sharp details? Is this website wrong? Sorry if I am beating a dead horse... But I need to buy a telescope based on specs and without prior firsthand experience.

December 30, 2007 05:01 AM Forum: Beginning Astronomy?


Posted By Jackie Pritchard

I have a WO Megrez 110mm ED telescope. My primary planned uses - after I get a alt-az mount and tripod which I am advertising for in AM - are visual and planetary/lunar with some casual DSO viewing.

What kind of filters would work best for a 110mm refractor given my intended uses? I am thinking first a moon or neutral density filter. I have seen them advertised at 13%, 18% and 25% in terms of light they let through. What are the pros and cons of more or less light let in (in terms of a 110mm refractor)?

I am thinking I would like a filter that blocks out some light pollution - like the Baader Moon & Skyglow filter.

I have a Baader fringe killer but I am not sure it will be of much use.

Any thought or suggestions? I will probably pick up a modest set of planetary filters down the road but I do not want to spend a lot for a special Mars or Venus filter. Thanks.

July 10, 2008 11:51 PM Forum: AstroMart FAQ

RSS feed disabled

Posted By Jackie Pritchard

I just started using Google reader and I tried adding RSS feeds for 4 categories in the Classified. Google shows each one with the wording "This RSS feed has been disabled". This is my FIRST ATTEMPT at doing RSS - what am I doing wrong???? Thanks.

April 11, 2009 11:22 PM Forum: Refractors

Celestron C102F vrs modern triplets?

Posted By Jackie Pritchard

I am wondering how the old Vixen/Celestron 102 fluorites made in the 1980s compare to modern apo triplets? I understand they were wonderful for their day and better than many/most modern doublets, but how would they compare to modern 4" triplets from Stellarvue or William Optics for example? Anyone with first hand knowledge?

April 24, 2009 08:09 PM Forum: Refractors

Opinions? TV60 vrs Tak FS-60C vrs SV70ED

Posted By Jackie Pritchard

Has anyone used 2 or more of these and can compare them? I know the TV and Tak are excellent quality, but can they overcome the disadvantage of having 10mm less aperture? My quandary: the TV and Tak are expensive for their size. If they would only give me a small advantage - say 10 or 15% - over a less expensive Stellarvue SV70, then I would opt for the Stellarvue. If they would give me a significantly better image - say 40%-50% - then I would consider biting the bullet and paying more for a TV or Tak. Now, I know one can't put exact percentages on this sort of thing. So basically, I am asking if spending significantly more money for a TV/Tak will equate with a significantly better view, or it will be a relatively small difference because the Stellarvue has more aperture and is a fine telescope itself? I have larger telescopes (80mm triplet apo & 4" fluorite refractor), so I am not interesting in opinions about the advantages of going to an 80mm or 90mm telescope. I want one of these 3 telescopes for travel and quick looks. I don't want to spend more than necessary, but I am willing to pay a premium IF WARRANTED. I can get the Stellarvue for hundreds less that the TV or Tak.

May 19, 2009 03:23 AM Forum: Mounts


Posted By Jackie Pritchard

I think I am looking for the impossible. I want a lightweight, inexpensive equatorial mount that accepts Vixen-style dovetails and has slo-mo controls. It needs to hold up to my 4" Celestron f/9 C102F, even when I am binoviewing - so I am guessing up to 15 pounds capacity. I know there are some good systems available but they seem to be either heavier or more expensive than I want. My criteria: 15 pounds or less total with weights and $250 or less used. I would like something that is mechanically very reliable and rugged. I am not thinking Ioptron, as I don't need the motors or fuss. I want something that I can push to a object, then engage the gears and use the slo-mo. Does any such mount exist? I do want to get my 4" Celestron up to 200X or more with stability. I can sometimes find either price or weight criteria met, but not both.

A second question that doesn't exactly jibe with the first because of the motors & not being a GEM: Anyone know if any of the Nexstar mounts (I know they aren't typically sold separately and they have motors) will support 15 pounds? Would a long tube refractor be limited in movement?


July 6, 2009 01:40 AM Forum: Refractors

Vixen ED115S or quality 4" refractor?

Posted By Jackie Pritchard

Anyone use a Vixen ED115S and can compare it to a quality 4" scope - say a Tak FS-102? I am just wondering what 15mm buys at this general size range? Do you need to go past 130mm or so to make a dramatic difference? I am thinking strictly visual and primarily for planetary and lunar observations.