184 replies to this topic

[MalVeauX]

Varies greatly, but an hour way there is some nice dark sky on the Blue Ridge Parkway in Southern Va.
I'm moving to an area that will be quite cloudy but also borders Bortle Class 3 skies.
30min from my door will be this facility
https://www.pari.edu
Anyway, I'm retiring in about 6 years and will gladly take long journeys to where the dark clear skies are out west.

All good,

 

Even with poor skies and light pollution, planetary is ready to go. Seeing is what matters though. Great seeing and high light pollution is fine! Again, for planets (most of the big close ones anyways). It's great to go for an excellent optical set, long focal-ratio or not, big aperture and all, but without excellent seeing, it will be a fuzzy mess rather than a sharp contrasty image of course. I think this is likely why lots of people use 4~5" ED/APO fracs as their planet scopes, to maximize the incoming light while keeping an aperture that reveals detail but doesn't require seeing levels that are excellent to see get a contrasty bright view (plus the lower setup time, no thermal acclimation really, etc, versus some huge heavy mirrors).

 

I think two scopes would be great, side by side or co-mounted. A 4" frac and/or a 10" newtonian with good optics, closer to F5 and F6 than F4 and a set of binos. Two options so that you can get nice views under poor and excellent seeing conditions, also happens to be great for all subject matter in the sky really. For cost, the 4" F11 ED's are low cost but offer very good views for this sort of thing. And if seeing is great, a 250mm F5~F6 will really show off.

 

Personally I use a 200mm F6 Quartz newtonian. I'd love to go bigger, but I also don't like the idea of ever moving something bigger outside of my observatory, so for non-obs scopes, I keep them portable enough. I also do not like dob-bases due to the materials, I'd want it to be all metal. I'm in Florida. Florida is not friendly to non-metal and I'm not about to baby some cheap particle/ply or whatever cheap dobs are made of, and I'm not spending top dollar on a custom dob. I'd rather have a beefy alt-az and keep it simple and fast with the 8" for now. Maybe one day I'll get a metal dob frame and go 16". But that's a big maybe.

 

 

 

 

 

Very best,

Edited by MalVeauX, 27 January 2020 - 09:00 AM.

[Asbytec]

I hope to have a 20"SST/Ostahowski f/3.4 in about 12 mo.

 

This summer I should have a unique 10" NMT/Pegasus f/3.4 DOB 

 

I've owned a 12" Orion dob that has been in pieces as I tried to repair the dead goto system.

 

Got an AT130 f/7 that sits too much because, as a DOB lover, I hate equatorial mounts. Has some nice planet views, a super value no question. Just not a KILLER at f/7.

 

Been thinking about a Sky-Watcher Skymax 180 f/15 but not many reviews here on CN.

 

I've reached out to Moonraker about his 150 Mak in development, turns out he's recovering from some illnesses and the Mak is new for him-gonna be awhile. Just love his work though.

 

SO-back to the purpose- what do you suggest for a Planet Killer?

Looking back at the OP, I have to say looks like you have all the bases covered. Pick one. Tell us. Except, maybe, for the one that sits too much not doing anyone any good. 

Edited by Asbytec, 27 January 2020 - 08:01 AM.

[Mike Spooner]

For me the #1 priority is an accurate figure - I've been satisfied with Newtonian planetary views from 6" up to whatever. The primary is the building block at the bottom of the wobbly stack, IMHO. The secondary is next (and often a problem for critical viewing) but smaller sizes can be replaced with less hassle and financial impact than the primary. Most of the remaining problems fall into what I would classify as mechanical/environmental effects, i.e. thermal, collimation, seeing, mounting, etc. 

 

So pick a size, get the primary right and work from there. My personal opinion concerning f/ratio and secondary size is they can be considered for 6 to 8" scopes as they are comfortable at f/10 or f/7 (for my height when Dob mounted). For larger scopes I like more comfortable f/ratios. With Paracorrs, modern eyepieces and collimation knowledge available having mitigated some of the old concerns, then we're back to the quality of the objective - still the base of the wobbly stack for me.

 

All opinions expressed here are my own and may have little resemblance to the majority available on CN. 

 

Mike Spooner

[Dougeo]

For me the #1 priority is an accurate figure - I've been satisfied with Newtonian planetary views from 6" up to whatever. The primary is the building block at the bottom of the wobbly stack, IMHO. The secondary is next (and often a problem for critical viewing) but smaller sizes can be replaced with less hassle and financial impact than the primary. Most of the remaining problems fall into what I would classify as mechanical/environmental effects, i.e. thermal, collimation, seeing, mounting, etc. 

 

So pick a size, get the primary right and work from there. My personal opinion concerning f/ratio and secondary size is they can be considered for 6 to 8" scopes as they are comfortable at f/10 or f/7 (for my height when Dob mounted). For larger scopes I like more comfortable f/ratios. With Paracorrs, modern eyepieces and collimation knowledge available having mitigated some of the old concerns, then we're back to the quality of the objective - still the base of the wobbly stack for me.

 

All opinions expressed here are my own and may have little resemblance to the majority available on CN. 

 

Mike Spooner

Thanks for bringing the original topic back on point

[Jeff B]

Late to the discussion but here are mine, a TEC 200ED and my Parallax/Zambuto 11" F7.  Rather than compete, they compliment each other.  

 

Around here, the seeing rarely supports an 11" aperture, so the TEC gets used more often.  When the seeing does support a larger aperture, I can get the Newt unbagged, the mount sync'ed and observing in under 10 minutes.  

 

For me, planetary viewing demands exceptional optics (and seeing!!) but also a "comfortable' viewing experience, which, again, for me, means being seated or standing comfortably.  I can do both with both scopes, making long sessions at the eyepiece a pleasure.

 

Also for me, I'm just addicted too my bino-viewers, especially for solar system objects.   I just see more and I find the viewing experience much more comfortable than mono-vision, and with my Denk power switch system, I can cycle through three different magnifications instantly.

 

For me, an excellent planetary newt has to have the following:

 

1. 8" - 12" aperture and I prefer F6 or slower focal ratios

2. Exceptional optics (including the secondary) that are smoooooth, with good coatings.

3. Central obstruction under 20% (pretty easy to do really, especially in slow scopes)

4. Excellent build quality which includes easy, precise collimation with the ability to keep collimation when pointed anywhere in the sky over the entire night and an excellent focuser.

5. An excellent thermal management system, which typically includes a BL fan.

6. Easy use of bino-viewers

7. A rotating tube if I use a GEM, for easy, comfortable eyepiece positioning and the ability to put my body down wind of the aperture.

 

Can't wait for Mars this year!

 

Jeff

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[CHASLX200]

Late to the discussion but here are mine, a TEC 200ED and my Parallax/Zambuto 11" F7.  Rather than compete, they compliment each other.  

 

Around here, the seeing rarely supports an 11" aperture, so the TEC gets used more often.  When the seeing does support a larger aperture, I can get the Newt unbagged, the mount sync'ed and observing in under 10 minutes.  

 

For me, planetary viewing demands exceptional optics (and seeing!!) but also a "comfortable' viewing experience, which, again, for me, means being seated or standing comfortably.  I can do both with both scopes, making long sessions at the eyepiece a pleasure.

 

Also for me, I'm just addicted too my bino-viewers, especially for solar system objects.   I just see more and I find the viewing experience much more comfortable than mono-vision, and with my Denk power switch system, I can cycle through three different magnifications instantly.

 

For me, an excellent planetary newt has to have the following:

 

1. 8" - 12" aperture and I prefer F6 or slower focal ratios

2. Exceptional optics (including the secondary) that are smoooooth, with good coatings.

3. Central obstruction under 20% (pretty easy to do really, especially in slow scopes)

4. Excellent build quality which includes easy, precise collimation with the ability to keep collimation when pointed anywhere in the sky over the entire night and an excellent focuser.

5. An excellent thermal management system, which typically includes a BL fan.

6. Easy use of bino-viewers

7. A rotating tube if I use a GEM, for easy, comfortable eyepiece positioning and the ability to put my body down wind of the aperture.

 

Can't wait for Mars this year!

 

Jeff

That 11" would be a killer in my seeing. My Starmaster 11" F/5.4 or F/5.6 i forget , could do 700x on my best nites.  Like i said, if i had one more shot at a planet scope it would be a 18" F/6 or 20" F/6 Dob.  Just as long as it will roll out the door all setup.  I grew up on ladder scopes with a 10" F/9.6 at age 14. While i only view planets that is not much moving around and ladder work to do. Also no Paracorr needed.   Shame my 18" F/5 Tectron had a soft mirror as it rolled out the door fine and the scope worked fine other than the mirror.  Did ok at lower powers for deep sky but at higher powers the planets always needed a turn of the focus knob to be sharp and they never would get sharp. 

Edited by CHASLX200, 27 January 2020 - 07:21 PM.

[Endymion]

https://evil.fandom....Space_Modulator

[stubeeef]

https://evil.fandom....Space_Modulator

I already have 2 of them, after Christmas sale at Big Lots.

[iKMN]

I says most any decent scope can be good for planets.  It takes patience and good seeing.  I am mostly a DSO observer but all my “best” or “memorable” views of the planets have been with a wide range of scopes that I just happened to be at the eyepiece with at the time when the conditions were just perfect.  Almost like the image just turned in a photograph for a few seconds.  Really awesome.  It takes patience though that I don’t have.  I’d rather be hunting galaxies but that’s me.  So I say a planet killer is whatever you want it to be.  Enjoy whatever you have.  It’s all fun.  

[TG]

While it is true that f/ratio has no bearing on optical performance, in terms of the whole system performing, it does matter:

 

- The depth of focus varies as the square of the focal ratio. Below f/5, fine focusers are required and even at f/5, achieving precise focus takes patience.

 

- Collimation becomes extremely important at faster f/ratios and the mechanical stability of the whole OTA and the mirror assembly in particular become important. Sloppy mirror cells and OTAs don't cut it any more.

 

- Faster f/ratios also have wider light cones. A larger sized flat is required to function at full aperture. This will lower contrast for planetary observing.

 

- Simpler eyepieces can't handle ratios faster than f/5 easily, the most common aberration being astigmatism

 

IMHO, f/5 is the fastest one should go if looking for a reflector of moderate aperture (say 8-14 inches) for planetary use. 

 

Tanveer.

[CHASLX200]

While it is true that f/ratio has no bearing on optical performance, in terms of the whole system performing, it does matter:

 

- The depth of focus varies as the square of the focal ratio. Below f/5, fine focusers are required and even at f/5, achieving precise focus takes patience.

 

- Collimation becomes extremely important at faster f/ratios and the mechanical stability of the whole OTA and the mirror assembly in particular become important. Sloppy mirror cells and OTAs don't cut it any more.

 

- Faster f/ratios also have wider light cones. A larger sized flat is required to function at full aperture. This will lower contrast for planetary observing.

 

- Simpler eyepieces can't handle ratios faster than f/5 easily, the most common aberration being astigmatism

 

IMHO, f/5 is the fastest one should go if looking for a reflector of moderate aperture (say 8-14 inches) for planetary use. 

 

Tanveer.

I like F/6 and slower as no Paracorr is needed and shallow focus starts to bother me at speeds faster than F/5.
 

[John Anderson]

From my experience, a fast 12" dob can have very good planetary images.

 

"Killer" planetary is subjective I guess but my inclination would be to go for aperture, even from an urban observing location.

 

Right now I don't have a scope but I'm considering either a 10" or 12" dob which would be used mostly for lunar/planetary under city skies.

 

My main issue is that I don't like the tiny exit pupil that comes from using a small refractor at high power ... but a 12" newtonian is just cruising at x200.

[Deep13]

Is the AT130 a refractor? I'd say built an alt-az head for it's tripod and use that.

[Deep13]

Is the AT130 a refractor? I'd say built an alt-az head for it's tripod and use that.

[stubeeef]

I love your signature btw

"That which can be asserted without evidence can be dismissed without evidence."

I have been looking for a nice Alt Az mount, a bit stuck between Losmandy and iOptron Cube Pro at the moment.

I love setting circles just fine, get me close and enjoy the hunt from there.

[luxo II]

Anyone using f/12-15 scope now on planets?

Yes... Maks... over the years two SW 180mm f/15, Santel MK91 (228mm / 3100mm f/13.5) and currently a superb APM/Wirth/Intes Mak (250mm / 3100mm f12.5) and an Intes-Micro M615.

The Santel is exquisite and it’s routine high power performance was what persuaded me to swap it for the APM/Wirth.

Only snag here has been the fires and abysmal weather over summer.

Edited by luxo II, 06 February 2020 - 05:46 PM.

[stubeeef]

I have been looking at the SW 180, but might wait till I have my other setups first.

 

I'll check into the APM, thanks.

[luxo II]

Stu, The only reasonable options for a large mak new are:

Sky-Watcher/Orion/Celestron 180mm f/15;
Questar 7”, $$$$$
Astrophysics 250mm, $$$$$ and a 20-year wait list;
Ottiche Zen, who only make the glass; you have to make the rest.

Last time I looked APM had an 11”, 16” and 20” - but the prices are eye-watering.

Intes and Santel are long gone from the market, though occasionally one pops up secondhand.

Edited by luxo II, 06 February 2020 - 11:22 PM.

[stubeeef]

ya, if man then 127or 180.

thx

[acochran]

A well figured 10" as has been mentioned. Some of my best views of Mars were with a 10 f/5.4. Saw dark volcanoes on Mars years ago with 8" f/7. Mars was high up, seeing was spectacular and scope was working well at 600x. My eyes were a bit better, too.

 

Mike Spooner

Ask Mike if he has any planet killers for sale. I looked through his 6" F10 a few years ago...OMG! Also, he has good seeing in the SW.

Andy

[ckwastro]

Mike’s 10” mirrors are killer too!

[donald41]

6" f/8!!!!!!!!!!!

[troyt]

In regards to size I believe 10" to be around the minimum but 12" - 16" is the sweet spot for most locations but this depends on your local seeing conditions of course.    

 

When it comes to design I have seen good images from these designs:

SCT and the variants (Edge etc)

Newtonian

DK

cassegrain

All designs have their quirks you just have to figure out what they are and how to overcome them to get the most out of your telescope.

I have to say the best telescope is the one you will use the most! 

 

Its worth mentioning the focal length of the telescope should be larger enough so the least amount of glass is used in the system. For example having the focal length large enough so you don't have to use a barlow! 

 

Attached is an image from a 11" edge telescope under under good conditions. Planet killers come in all shapes and sizes as long as you have the skills.  

 

 

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[a__l]

C11 before purchase they require testing on an interferometric stand

Next three options
1. Good
2. Adjust, check, good.
3. Adjust, check, reject.

Edited by a__l, 17 February 2020 - 06:49 PM.

[Subaru45]

My killer would be a reflector, made by Ed Grissom, like the one found in 'Best of reflectors thread', 'refractor vs reflector ', by Daniel Mounsey. Any size would probably be fine, but his 13" sounds to be just about right !