Return to the Cloudy Nights Telescope Reviews home pageAstronomics discounts for Cloudy Nights members
· Get a Cloudy Nights T-Shirt · Submit a Review / Article

Click here if you are having trouble logging into the forums

Privacy Policy | Please read our Terms of Service | Signup and Troubleshooting FAQ | Problems? PM a Red or a Green Gu… uh, User

Equipment Discussions >> Reflectors

Pages: 1 | 2 | 3 | 4 | (show all)
Gray
scholastic sledgehammer
*****

Reged: 01/31/11

Loc: Hixson, TN
Re: Planet scope decision new [Re: george golitzin]
      #5615958 - 01/10/13 05:57 PM Attachment (25 downloads)

George, I see you have canceled the refractor due to the lack of aperture. I am interested in a good planetary telescope, that may double as an imager but not particularly at this time. I feel I may agree with you on this and thusly take it off my list.

Ed D's suggestion of having the mirror tested and if warranted re-figured and re-coated is another good idea. I looked for about 30 minutes of where I could send my mirrors too ,and how much I would be looking at, but I seem to have hit a road block due to the small size of the mirror. I found one source that would re-test and re-work my mirrors for around 450$~.

My Moonlight is only a single speed focuser, and I think I can keep it that way all things considered

Mr. Issacs, I thank you for your commentary with generous thoughts and ideas that are more important to the subject than just buy another scope and be done with it! I agree 100% with you that I should at-least have a fan on my scope and have read proofs that they can make a huge difference. That will be my first step. I will need to find a supplier for that accessory (on the cheap if possible).
So it seems I'm at the point first and foremost to actually test this scope of mine first and see how it preforms before making any further telescope purchases, which is responsible sounding enough to me . I pulled a post from the achieves about the Parks AV8 system but found no real help here. http://www.cloudynights.com/ubbarchive/showflat.php/Cat/0/Number/1319195/page... One comment about half way down (may be a mis quote) says that an 8"F5 is more of a "general observing" type telescope than a planetary. That kinda talk suckers me into believing a long focus newt is the way to go, and not just a 6" but an 8" just like the AV8 (8" F6). So, I have three options now with the refractor being removed henceforth.

1) Run tests on what I have now with a fan installed to determine if I have a general observing scope or better.
2) If not send mirrors off for reworking in hopes of a better wave rating.
3) Look into either the 6" or 8" F8/F6 Parks Newt's as a better alternative. Or lastly, check into the Ioptron 150mm Mak instead.

If I could remove the Mak from the list I would. Cool down time is not too critical although tube currents would be, but how it would compare to the Parks 6" newt should determine if it stays or goes. Any more thoughts in line with my rambling is very much appreciated!

Edited by Gray (01/10/13 06:06 PM)


Post Extras: Print Post   Remind Me!   Notify Moderator  
Gray
scholastic sledgehammer
*****

Reged: 01/31/11

Loc: Hixson, TN
Re: Planet scope decision new [Re: Gray]
      #5616007 - 01/10/13 06:24 PM

I forgot to mention that I have taken note of the upgrades suggested by rflinn68! Awesome advice, thank you sir. Also, I agree with you too Jeff, If I had the time and I should one day, I would just attempt my first mirror project!

Post Extras: Print Post   Remind Me!   Notify Moderator  
Jon Isaacs
Postmaster
*****

Reged: 06/16/04

Loc: San Diego and Boulevard, CA
Re: Planet scope decision new [Re: Gray]
      #5616147 - 01/10/13 07:44 PM

Quote:

I will need to find a supplier for that accessory (on the cheap if possible).




I tried making my own fans but I never really was able to eliminate the vibration. I recommend Floyd Blue's fans, they are simple, effective and free of vibration. I have 4 of them, the most recent is for my 8 inch F/5 and I also have my 10 inch f/5, my 12.5 inch F/4.06 and my 12.5 inch F/6 fitted with Floyd's fan.

Blue Sky Accessories: Floyd Blue, Blueman

If I recall correctly, they're about $35.

Jon


Post Extras: Print Post   Remind Me!   Notify Moderator  
dpwoos
Pooh-Bah
*****

Reged: 10/18/06

Loc: United States
Re: Planet scope decision new [Re: Jon Isaacs]
      #5616522 - 01/10/13 11:55 PM

Our 6" f/8 flex mirror dob has, out of necessity, a fan that blows across the face of the mirror. That worked so well that now all of our newts have fans that blow across the face. We mount the fan(s) on the same 1/2" neoprene rubber that we use for our flex cells, and I have never detected any vibration. We use good quality pc cooling fans with filters.

Post Extras: Print Post   Remind Me!   Notify Moderator  
Gray
scholastic sledgehammer
*****

Reged: 01/31/11

Loc: Hixson, TN
Re: Planet scope decision new [Re: dpwoos]
      #5617205 - 01/11/13 12:38 PM

Thanks for the fan help Jon & dpwoos. I'm thinking it would be a bit difficult to cut a hole in the side of a metal ota, so more than likely for now I will just install one on the back of the mirror.
I've been looking into what actually constitutes a good planetary scope or more so optimizing a scope for planetary viewing. It seems some agree that focal ratio is not important in reflectors but central obstruction is. Seeing, optics ,and thermal issues being the most critical. Still, I see posts from older gentlemen wishing they still had a long focus newt from the days past. Those kinda comments I can empathize with and appreciate as good as gold. I've taken all this into account and still am lusting after a long focus newt "optimized" for plants. I guess I'm looking at a 6" f8 long tube newt preferably with a curved spider, dual speed focuser, fans, and flocking. If there is any other scope out there that would be better at observing Jupiter and so on, I sure would like to know. I haven't read a good thing once about Ioptron's 6" Mak yet, so the axe must come down on it too. lol

Edited by Gray (01/11/13 12:39 PM)


Post Extras: Print Post   Remind Me!   Notify Moderator  
azure1961p
Postmaster
*****

Reged: 01/17/09

Loc: USA
Re: Planet scope decision new [Re: Jeff Morgan]
      #5617232 - 01/11/13 12:52 PM

I'd personally get that 8" f/9 truss dob by Optcorp. Nothing in your want list could touch it. Too the mount would be much easier on you than the PARKS. At anyrate Id go with the 6" f/8 or the 8" f/9 both will yield very high definition in good seeing. The only thing I've seen outdo the 8" f/9 was a 10" f/7 Cave and another one bring a Parks and a Celestron C11. Not a Meade10" SCT nor 8" SCT. Those have been my experiences anyway.

Oh and collimating is NOT the bother it is with short scopes. It still matters to be sure but the disaster factor is lessened.

Pete

Edited by azure1961p (01/11/13 01:02 PM)


Post Extras: Print Post   Remind Me!   Notify Moderator  
Gray
scholastic sledgehammer
*****

Reged: 01/31/11

Loc: Hixson, TN
Re: Planet scope decision new [Re: azure1961p]
      #5617325 - 01/11/13 01:56 PM

Pete, the only problem I'd have with that 8" F9 Dob is the tracking platform I'd have to buy. I really don't have space for that type of thing right now. Don't get me wrong though, I'd love to look through that instrument, but chasing a planet back and forth gets old.

Post Extras: Print Post   Remind Me!   Notify Moderator  
dpwoos
Pooh-Bah
*****

Reged: 10/18/06

Loc: United States
Re: Planet scope decision new [Re: Gray]
      #5617404 - 01/11/13 02:51 PM

Not to say that you aren't entitled to your own likes/dislikes etc., but whenever someone posts that they have difficulties tracking with a dob I have to wonder if they have ever given this a chance with a properly constructed mount, with minimal stiction. Many, many folks find tracking planets at high powers not to be that big a deal, and so maybe this is worth a rethink?

Post Extras: Print Post   Remind Me!   Notify Moderator  
Starman1
Vendor (EyepiecesEtc.com)
*****

Reged: 06/24/03

Loc: Los Angeles
Re: Planet scope decision new [Re: Gray]
      #5617405 - 01/11/13 02:51 PM

The three "C"s of observing:
--Collimation. If you're not real certain on this one, getting good tools (e.g. Catseye or Glatter) can make the difference. Adequate collimation is OK but excellent collimation is required for small planetary details.
--Cooling. No 8" will cool by itself to ambient temperature if the temperature is falling during the night. At best, it will take 3 hours or more before heat issues disappear from the images. Active cooling is mandatory.
One rear fan will cut the period of cooling to 1/3 of what it would be without the fan. This is critical for planetary observations.
--Conditions. Seeing, mostly, and transparency. Seeing is the Biggie. I have seen nights where my 12.5" was aperture-limited and the images unbelievable. In those conditions, I've seen Jupiter with as much detail as a really good photograph. No, better, because what I saw was sharply focused and photos never are.

Collimation and cooling are within your control. Conditions are not, but there are some lessons to be learned:
--never observe an object directly above a roof top. Heat from the roof will rise and distort the image.
--seeing conditions are often best at 2 times of night: right at twilight in the evening when the heat of the sun is removed from the atmosphere; and between midnight and dawn when the atmosphere has settled into strata of temperature gradients.
--try not to sit with your warm legs directly below a steel tube. You will see heat signatures in the images. It helps to flock the tube internally. This won't slow the cooling of the tube, but it will reduce the heat images from warm legs under the tube, and it will help reduce tube currents as the steel tube loses its heat into the interior.
--resist the temptation to look at an object below 30 degrees altitude. At 30 degrees, you are looking through literally twice as much air as at the zenith, and the extra air will always show more turbulence and scintillation. Of course, with Venus and Mercury, this rule doesn't work, but for exterior planets, this is a good rule to follow.
--the center of a valley usually has steadier air than the periphery (where air is either rising or falling). I went from the center of West LA, where seeing was spectacularly good, to a mountainside above LA. Now I see good seeing one or two nights a year. If it has to be a mountainside, make it one facing the wind, not the "alee" side. a steady laminar flow over your site is much better than the turbulence after the air rolls over some form of obstruction. In a city, try to set up on the upwind side of a building for the same reason.
--look at the weather maps. 2-3 days after a front passes, the air gets calmer and more stagnant. If the pressure isobars are close together, seeing will suffer.
--check out the jet stream position. If it's overhead (+/- 50 miles), you won't get good seeing. If it's a long way away from overhead, you might.
--check out the high altitude wind speed. If it's dead calm or if it's really fast, you won't get good seeing. If it's steady and not too fast, the air flow may be quite laminar and good seeing will result.
If you learn to anticipate good seeing conditions, you will be rewarded with a lot more episodes of fantastic planetary images.

Prevent stray light from entering the bottom of the eyepiece bya adding about an 8-10" extension to the side of the tube opposite the focuser. This will improve contrast (like flocking does to the interior) by keeping direct light from the sky out of the bottom of the eyepiece in the focuser. It can be quite simple--even black construction paper or cardboard.

Last, I don't see anything wrong with an 8" f/5 on an EQ mount for planetary viewing. Of the scopes you mentioned, the Parks isn't available, the 6" Mak is nice but it'll be a gamble that you get a really superb one optically (and cooldown is WORSE than your 8" newt.). And the Skywatcher refractor is too small to show you the small details the 8" can (the 8" will resolve details 1/2 the size).


Post Extras: Print Post   Remind Me!   Notify Moderator  
Gray
scholastic sledgehammer
*****

Reged: 01/31/11

Loc: Hixson, TN
Re: Planet scope decision new [Re: Starman1]
      #5617510 - 01/11/13 04:01 PM

dpwoos, I did have a Z12, and after a couple of observing sessions during decent seeing, I grew uncomfortable constantly bringing the planet back only too be able to observe the object for maybe a second in the sweet spot. I don't discount what others can do or have been able to do, I'm just saying it's not for me. I appreciate your thoughts.

Don, so glad you stopped in to enlighten me further! I gather from what you say that Parks is no longer in business, even though their site is up and current? Now then it looks as if I should just upgrade my newt with fans, flocking, and I'm wondering what you guys think of a curved spider? 3 or 4 vane. I was thinking 3, for my 8" even though they are expensive at $94 from Jim at Scopestuff. I'm also wondering if I should replace the secondary or keep it. What would you suggest I upgrade my scope with altogether, for optimizing it for planets is a better question of questions. Or would another scope be a better option? Thank you Starman

Edited by Gray (01/11/13 04:03 PM)


Post Extras: Print Post   Remind Me!   Notify Moderator  
Starman1
Vendor (EyepiecesEtc.com)
*****

Reged: 06/24/03

Loc: Los Angeles
Re: Planet scope decision new [Re: Gray]
      #5617531 - 01/11/13 04:14 PM

Quote:

I gather from what you say that Parks is no longer in business, even though their site is up and current? Now then it looks as if I should just upgrade my newt with fans, flocking, and I'm wondering what you guys think of a curved spider? 3 or 4 vane. I was thinking 3, for my 8" even though they are expensive at $94 from Jim at Scopestuff. I'm also wondering if I should replace the secondary or keep it. What would you suggest I upgrade my scope with altogether, for optimizing it for planets is a better question of questions. Or would another scope be a better option? Thank you Starman



Parks' website is pre-paid but there is no one currently working there.
If you do a curved spider, be aware that most of them are not collimationally stable. Try the ones that look like )-( as in this site (go down the page--the pic is on the right):http://www.obsessiontelescopes.com/telescopes/12.5/index.php
That design does not appear to sag as you point lower.
Might as well keep your secondary.

If you upgrade the scope but keep it possible to use your mounts, an 8" f/6-f/7 would still work and the secondary would be a little smaller.
An f/9 would be getting somewhat heavy and too big a wind sail, not to mention having an inconvenient eyepiece position for comfortable viewing.
Frankly, by today's standards, f/5 is long. Imaging scopes are typically f/3-f/4.

And, as long as your scope tracks, you'll not need a coma corrector at f/5.


Post Extras: Print Post   Remind Me!   Notify Moderator  
rflinn68
Carpal Tunnel


Reged: 03/09/12

Loc: Arkansas
Re: Planet scope decision new [Re: Gray]
      #5617539 - 01/11/13 04:19 PM

The Destiny 3 vane curved spider worked very well for me. I went ahead and did the flockboard from Protostar and put on a new 1/20 ptv Antares Optics secondary at the same time. My collimation holds just as good or better than it did before with the factory spider. The Destiny that I bought was about the same price but it also came with collimation thumb screws. Not sure if Jims do or not. I also got lucky with Antares Optics! I ordered the 1/15 ptv 2.6" secondary for my 10" and they were out of that one and out of the 1/18 so they shipped me a 1/20 mirror for the same price of a 1/15. Very good people to deal with for sure! Like I said before, I almost sold my scope but now I am so glad I didnt. I'm still wanting to get a big dob (16"+) and will start saving for it soon but I am quite happy now with my 10" for the time being.

Post Extras: Print Post   Remind Me!   Notify Moderator  
rflinn68
Carpal Tunnel


Reged: 03/09/12

Loc: Arkansas
Re: Planet scope decision new [Re: rflinn68]
      #5617569 - 01/11/13 04:35 PM

I just checked and the thumbscrews are an option at ScopeStuff. I bought the Large from Destiny for $99 and they were standard. The Large 3 vane is $109 at ScopeStuff and the thumbscrews are extra. The medium 3 vane is $94. A medium now from Destiny is $69.95 but you'll need to see what options are included with it.

Post Extras: Print Post   Remind Me!   Notify Moderator  
Gray
scholastic sledgehammer
*****

Reged: 01/31/11

Loc: Hixson, TN
Re: Planet scope decision new [Re: rflinn68]
      #5617574 - 01/11/13 04:39 PM

Thanks rflinn68!

Post Extras: Print Post   Remind Me!   Notify Moderator  
Gray
scholastic sledgehammer
*****

Reged: 01/31/11

Loc: Hixson, TN
Re: Planet scope decision new [Re: Gray]
      #5617903 - 01/11/13 07:59 PM

I really appreciate all you fine fellows who have offered to help me with this interesting decision. It is fascinating to think of all the possibilities and humbling when I see how much money the good things cost. I hope others will read this and learn a bit from what I've seen wrote so many times before. I've learned quite a bit from all of this and am very thankful to you all. I'll end this thread with that.

Post Extras: Print Post   Remind Me!   Notify Moderator  
Jeff Morgan
Postmaster
*****

Reged: 09/28/03

Loc: Prescott, AZ
Re: Planet scope decision new [Re: Starman1]
      #5618083 - 01/11/13 09:55 PM

Quote:


If you upgrade the scope but keep it possible to use your mounts, an 8" f/6-f/7 would still work and the secondary would be a little smaller.
An f/9 would be getting somewhat heavy and too big a wind sail, not to mention having an inconvenient eyepiece position for comfortable viewing.
Frankly, by today's standards, f/5 is long. Imaging scopes are typically f/3-f/4.

And, as long as your scope tracks, you'll not need a coma corrector at f/5.





Rebuilding a commercial dob allows one to spread the money over time. Doesn't help resale though. The economics aren't that compelling, at that point DIY starts making a lot of sense. 50/50 call on that, there is a lot of value in being able to get into the game now vs. months from now.

The 8" f/9 in the link was a truss design, it's performance in the wind likely is reasonable. It would have a zenith eyepiece height of 72" (give or take a few, depending upon the build). The OP was interested in planets, and listed his location as Tennessee. Not much chance of a planet finding it's way to the zenith from that latitude. Close (perhaps 75 degrees elevation), but not quite. Might even be quite comfortable for someone of average height. (Then again, the OP could be short.)

If planetary is your thing, look at what the more prolific ALPO observers such as Troiani, Parker, and Beisch are using - Large Newtonians in the f/6 to f/7 range. First emphasis on aperture, second emphasis on long. I doubt many (or any) of them are sub f/5, even for planetary imaging. Especially for planetary imaging where image scale is desired.

Edited by Jeff Morgan (01/11/13 10:17 PM)


Post Extras: Print Post   Remind Me!   Notify Moderator  
Gray
scholastic sledgehammer
*****

Reged: 01/31/11

Loc: Hixson, TN
Re: Planet scope decision new [Re: Jeff Morgan]
      #5618501 - 01/12/13 06:24 AM

Jeff, that is an excellent observation and yes the planets do not reach zenith at my location, more like what you guessed, at most 75 degrees. I do have a badder mpcc and an at ff as coma correctors, but have only used the badder yet with good results. With the truss design I would need a tracking platform and I do not wish to go that route at this time. I was looking around and if I actually wanted a 6" F8 newt, I would have to buy an Orion dob and put rings on it for around $300. I'm not sure I want to do that, but it is an option. Looking at a set of rotating rings, they will run me $450 for an 8" set. I've never used any before and wonder if they are worth it. I'm thinking my 8" should be tested out first, then flocked, fanned, and maybe a new spider with a set of Parallax rings. This is off topic but I would also like a instrument on a alt/az mount for comet scanning. I'm thinking either a 10" dob or a set of big bino's on a good mount, also need a good chair. Plant scope is almost concluded here with me. Thanks again Jeff!

Post Extras: Print Post   Remind Me!   Notify Moderator  
Jon Isaacs
Postmaster
*****

Reged: 06/16/04

Loc: San Diego and Boulevard, CA
Re: Planet scope decision new [Re: Gray]
      #5618520 - 01/12/13 06:52 AM

Graham:

A few thoughts:

- For correcting coma at planetary magnifications, the Paracorr is the one. It is my understanding that the MPCC adds spherical aberration and is basically for astrophotography.

- All total summed effect of all the modifications you can do will be small in comparison to just making sure that your current scope is perfectly collimated and thermally stable. The first step IMHO, is doing the small things which make big differences in getting your current scope to perform it's best.

- When you listen to old timers, you are listening to people who have memories of how things used to be rather than how they are today. Back in the old days, there were no coma correctors, eyepieces had problems with fast mirrors, and fast mirrors were generally not well made. The world has changed...

Jon Isaacs


Post Extras: Print Post   Remind Me!   Notify Moderator  
Gray
scholastic sledgehammer
*****

Reged: 01/31/11

Loc: Hixson, TN
Re: Planet scope decision new [Re: Jon Isaacs]
      #5618527 - 01/12/13 07:15 AM

LOL, wow, never would've expected that comment! Thanks for that tid bit on the coma correctors too. Paracorr, check. I do have a laser and a Cheshire but maybe I should look into better tools. I will check them out. I'll do further reading about rotating rings before I decide on them too. Fans are a biggie and I will also read what I should do there. I appreciate your thoughts Jon.

Post Extras: Print Post   Remind Me!   Notify Moderator  
Jon Isaacs
Postmaster
*****

Reged: 06/16/04

Loc: San Diego and Boulevard, CA
Re: Planet scope decision new [Re: Gray]
      #5618547 - 01/12/13 07:43 AM

Quote:

I do have a laser and a Cheshire but maybe I should look into better tools.




A good laser is a good tool.. What laser are you using and are you Barlowing it to adjust the primary.

Jon


Post Extras: Print Post   Remind Me!   Notify Moderator  
Pages: 1 | 2 | 3 | 4 | (show all)


Extra information
21 registered and 30 anonymous users are browsing this forum.

Moderator:  ausastronomer, Phillip Creed, JayinUT, okieav8r 

Print Thread

Forum Permissions
      You cannot start new topics
      You cannot reply to topics
      HTML is disabled
      UBBCode is enabled


Thread views: 3998

Jump to

CN Forums Home


Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics