As I get older, I'm finding a more "Grab & Go" telescope has been more and more the way I want to go as I do more observing that way. I have a Tele Vue 85 which I use constantly with a Discmount-4 mount on a Gitzo tripod- usually in my backyard. I'm thus asking my fellow Astromarters, should I possibly get a lightweight 5"-6" Mak-Cassegrain (Orion's?)to complement my 85? Right now, I also have a 4" Genesis SDF which I bought a few years ago here on Astromart. I use it on occcasions but I feel it doesn't show much more than my 85 and , to see fainter objects, I should move up to more aperature than the 4", realizing that the Genesis is a classic scope. I'd appreciate any thoughts any of you may have because it would mean I would sell the Genesis. Tom
GENESIS SDF vs. 5"- 6" MAK-CASSEGRAIN
Started by ThomasN, 02/27/2010 01:38PM
Posted 02/27/2010 01:38PM
Opening Post
Posted 02/27/2010 03:04PM
#1
Back when I first bought my TV102, it went side-by-side with my ETX125 a few times. The ETX has more than twice the f.l. of the 102 and could easily reach high magnifications. But it needed high magnification to equal the 102.
Again and again I found that I could see the same details and split the same double stars in both scopes if I used the same eyepiece in both. If I tried to make the magnifications equal, the TV102 showed more detail and did a better job splittting doubles.
There were differences, however. The 102's image always seemed cleaner...when BOTH scopes were showing the same level of detail (ETX at much higher magnification). With both scopes at the same magnification, both were sharp but the ETX image lacked detail.
Also, the ETX, as would be expected, did better on globular clusters. The images were brighter and the scope did a better job at resolving the cluster. In comparison, the 4" refractor lagged badly.
I would suggest you choose a Mak with at least 6" aperture.
Bob
Again and again I found that I could see the same details and split the same double stars in both scopes if I used the same eyepiece in both. If I tried to make the magnifications equal, the TV102 showed more detail and did a better job splittting doubles.
There were differences, however. The 102's image always seemed cleaner...when BOTH scopes were showing the same level of detail (ETX at much higher magnification). With both scopes at the same magnification, both were sharp but the ETX image lacked detail.
Also, the ETX, as would be expected, did better on globular clusters. The images were brighter and the scope did a better job at resolving the cluster. In comparison, the 4" refractor lagged badly.
I would suggest you choose a Mak with at least 6" aperture.
Bob
Posted 02/27/2010 08:02PM
#2
I once put a 4" APO up against a 6" Russian Mak-Cass side-by-side. The
high-power views were pretty much identical. Except that the Mak
took much longer to cool-down. I eventually sold the Mak,
because I just didn't see any point to it. I think Mak-Cass
in this 5" - 6" size range are a good alternative to much more
expensive 4" APOs. But if you've already got an APO you
are happy with, it just doesn't make sense.
What about something like a Celestron C8 SCT? They are pretty
light weight, MUCH more aperture than a 4" APO, and they are
making some pretty nice ones these days. There are still
some cool-down issues, but its about the same as a 6" Mak-Cass.
I think thats a more interesting alternative. Recent model
used ones can be had for maybe $400 - $600.
high-power views were pretty much identical. Except that the Mak
took much longer to cool-down. I eventually sold the Mak,
because I just didn't see any point to it. I think Mak-Cass
in this 5" - 6" size range are a good alternative to much more
expensive 4" APOs. But if you've already got an APO you
are happy with, it just doesn't make sense.
What about something like a Celestron C8 SCT? They are pretty
light weight, MUCH more aperture than a 4" APO, and they are
making some pretty nice ones these days. There are still
some cool-down issues, but its about the same as a 6" Mak-Cass.
I think thats a more interesting alternative. Recent model
used ones can be had for maybe $400 - $600.
Funding Member
