Posts Made By: Mark Peterman

Thanks for all the replies and the link to the Mel Bartles secondary calculator. I have attached a photo of the results using both mirror sizes.

The columns show a list of off-axis radius, the ilumination for this circle and the light loss in magnitudes. If the illumination falls below 70%, that line is shown in red.

The Tele Vue website lists the 24mm Panoptic as having a field stop of 27mm which would be a radius of 13.5mm. Looking at these results, does that mean that I would still have over 75% illumination across the whole field with that eyepiece and a 2.1" secondary? (roughly 95% illumination with the 2.6" secondary)

With this additional information, are there any other thoughts on the benefits of (or not) switching to a 2.1" secondary on this scope?

Thanks,

Mark

P.S. I'm learning from the feedback and hopefully others will benefit too.

A quick Google on filter+numbers turned up this on photonotes.org

Wratten numbers.

A series of numbers used to describe colour conversion and other filters, used by some filter manufacturers.

Frederick Wratten was a British inventor who developed a fairly arbitrarily-numbered series of colour filters a century ago. His company was bought by Kodak in 1912, which continued manufacturing his filter products under the Wratten name.

As noted, individual filter numbers (particularly letter grades) are inconsistent and quite arbitrary. However they do follow a general structure of categories, as follows. Sometimes filter makers other than Kodak will supply Wratten equivalent numbers, though they may use their own numbering schemes.

2-15. Yellow filters.
These filters run from pale yellow to deep yellow.

16-32. Orange, red, magenta filters.
The most common in this range is probably red 25.

34-61. Violet, blue, green filters.
80A-80D. Cooling (blue) colour conversion filters.

85N3-85C. Warming (amber) colour conversion filters.

81-81D. Warming (light yellow) light balancing filters.

82-82C. Cooling (light blue) light balancing filters.

87-106. Miscellaneous.
The 87, 87C and 89B infrared filters (opaque to visible light) are probably the most common filters in this range along with the 96 range of neutral density filters.

cf. cooling filter, decamired, filter, gel, infrared, neutral density filter, opaque, warming filter.

FYI,

Meade now has more photos and specs on the LightBridge Truss scopes on their website.

http://www.meade.com/lightbridge/index.html

Also, check out this website, they show specs for a 16" listed there.

http://www.bintel.com.au/MeadeLightbridge.html

If looking for a secondary mirror, who's the best?

Protostar uses Dielectric coatings.

What about Antares?

When ads mention "Enhanced" coatings, are they talking about Dielectric coatings?

Mark

I owned one of these from 1998 - 2000. It was a great scope. I never had to bend the stalk to get the secondary aligned but I did have to "shim" it a bit with a washer between the stalk and the tube.

Mark

Thanks guys - I appreciate the help.

Check out Skytools 2

http://www.skyhound.com/skytools.html

If I'm not mistaken, NEWT asks YOU how much in-focus you want from the focal plane. With your entry, NEWT will determine the location/measurements of the rest of the scope from there.

I contacted the first sellar and asked if he would consider any type of compensation for the missing adapter. Shortly after, he refunded me an amount that I believe is fair. So I am satisfied.

The item from the second sellar finally arrived and it was not shipped priority. I contacted the sellar and pointed out our agreement was USPS Priority (which would of actually cost him less than he ended up paying). He apologized and said that it was just an oversight on his part and promptly sent me a refund for the shipping.

Both sellars made their mistakes right and I appreciate that. 5 stars to both of them.

Mark