Are these mirrors any good?

Are the mirrors at the below site any good? I don't have a clear
understanding of what the specs on them mean so I don't know if these
are worth it or not, but the prices seem low. Or, are they low for a
reason?

http://www.chapmansltplus.com/tele.htm

"5kdz" wrote in message ...
Are the mirrors at the below site any good? I don't have a clear
understanding of what the specs on them mean so I don't know if these
are worth it or not, but the prices seem low. Or, are they low for a
reason?

http://www.chapmansltplus.com/tele.htm



They are very thin and since it is not stated that they are annealed pyrex
then it can be assumed they are plate glass. This would be fine with me if
they were thicker but it seems to me that the figure of the mirror may be
significantly affected by temperature changes since they are all
substantially less than an inch thick.


--
Martin
http://home.earthlink.net/~martinhowell

Are the mirrors at the below site any good? I don't have a clear
understanding of what the specs on them mean so I don't know if these
are worth it or not, but the prices seem low. Or, are they low for a
reason?

4.5 inch mirror, $10, 6 inch mirror $25....

I like the 8 inch F4 mirror for $70.... Of course it has a 750mm focal length,
making it actually F3.75. This same mistake was made previously by someone
selling these mirrors on EBay.

Looks like the same Ebay stuff to me, though for $25 you could always use the 6
incher to start fires.

Jon

(Jon Isaacs) wrote in message ...

Are the mirrors at the below site any good? I don't have a clear
understanding of what the specs on them mean so I don't know if these
are worth it or not, but the prices seem low. Or, are they low for a
reason?

4.5 inch mirror, $10, 6 inch mirror $25....

I like the 8 inch F4 mirror for $70.... Of course it has a 750mm focal length,
making it actually F3.75. This same mistake was made previously by someone
selling these mirrors on EBay.

Looks like the same Ebay stuff to me, though for $25 you could always use the 6
incher to start fires.

Or shaving (for those of us who shave).

Thad Floryan wrote:
(Jon Isaacs) wrote in message ...

Are the mirrors at the below site any good? I don't have a clear
understanding of what the specs on them mean so I don't know if these
are worth it or not, but the prices seem low. Or, are they low for a
reason?

4.5 inch mirror, $10, 6 inch mirror $25....

I like the 8 inch F4 mirror for $70.... Of course it has a 750mm focal length,
making it actually F3.75. This same mistake was made previously by someone
selling these mirrors on EBay.

Looks like the same Ebay stuff to me, though for $25 you could always use the 6
incher to start fires.


Or shaving (for those of us who shave).

OK. Everyone is confirming what I suspected.

Looking at the other side of the question, can someone suggest a source
for decent, (not great, just decent) inexpensive, light weight 4 or 6
inch parabolic mirrors if I wanted to experiment with constructing a
short focal length ultra-light backbacking telescope?
[I know I could grind my own; there're even local classes, but then I
suspect I'd put way more effort in a good figure than this experiment
deserves - I can always return to grinding a top notch mirror if
whatever I build functions well otherwise.]