Which scope for planetary f10 / f12 / f15

[Charlie 2436]

Hi everyone I am looking for a scope to do planets and lunar observing and am a bit unsure as to the difference between an f10 / f12 or f15 apart from focal length, what difference would the observer notice between the different scopes.

 I have been looking at FLO’s 80mm f12 or f15 scope tech and the 80mm f10 Stella Mira, and I am unsure as to what the difference would be to the observer between the f10 or the f15, ie would the image be bigger or brighter ? Why go for an f15 if an f10 is just the same ?. the Stella Mira is an ED scope but I don’t know if that would make much of a difference.

 I have a SW 127 mak at the moment and was wondering if any of these scope’s would give me a better experience, or would I be better going for the 180 mak.

thanks Robert 

[johninderby]

In general the longer focal lengths are beter on lunar / planetary and have the added benefit of being able to use cheaper eyepieces as long focal lengths don’t require top quality eyepieces.

The Scopeyech 80 f/15 and Stellamir 80 f/10 are pretty much a tie on the moon with the StellaMira having a small edge on planetary. I have the ScopeTech and find it is an exceptional performer on the moon and planets. Used to have the StellaMira but sold it to help fund a 125mm APO.

I also used to have a Skymax180 but now replaced with a Classical Cassegrain 8” which has a lot of advantages such as quick cooldown and no dewing problems and has a proper focuser and will take higher magnification.

https://www.firstlightoptics.com/stellalyra-telescopes/stellalyra-8-f12-m-lrs-classical-cassegrain-telescope-ota.html

The Skymax127 is quite a good lunar / planetary scope though. The reason for going for a refractor is just that I like using one although an 80mm refractor isn’t going to give better images than the 127 mak.

First image taken with the ScopeTech and a smartphone and the second taken with the StellaMira and a smartphone.

Edited March 30, 2021 by johninderby

[John]

I don't think any refractor short of (maybe) an ED120 would give you a better experience for planetary observing than your 127mm mak-cassegrain.

 

[Charlie 2436]

Thanks for your advice guys. It looks like I will have to wait until the SW180 mak is available and also look into the classical cassegrain. I hope that they will be an improvement over the 127mak. Do you think that the 1” extra on the classical cassegrain would make much of a difference or is it that it’s a different type of scope that makes the difference.

[Charlie 2436]

PS I liked the photos of the moon ,I don’t seem to be able to get any good photos with my phone. Was that with the f12 or f15 scope tech ? John 

thanks Robert 

[johninderby]

The big advantage of the Classical Cassegrain is no corrector plate on the front. The CC will cool down in about half an hpur whereas the 180 mak will require a few hours. Also no dewing problems.The CC has a fixed primary mirror unlike the mak so no mirror movement. Also having a proper dual speed  crayford focuser makes a huge difference in focusing. I did upgrade the stock crayford with a Baader Steeltrack though.

The first photo is with the Scopetech f15 and the second is with the StellaMira f10.

Photo comparing the size of the 180 mak and the CC8” plus photos of my CC8” which is the TS version but identical to the StellaLyra except for the colour.

 

 

[michael.h.f.wilkinson]

I agree that no 80 mm is going to best a 127mm mak-cas on planets. Even my 6" Schmidt-Newton is way better on the moon and planets than my 80 APO triplet, and that is not primarily a planetary scope. A long focal length achromat is not going to best a good quality apo or ED scope with a faster focal ratio in my experience (although they can certainly come very close or perhaps even equal them). Especially in imaging, aperture is king on planets.

Regarding cool-down time: store the scope in an unheated room or garage, and it will reach ambient temperature much quicker. Also, the Schmidt corrector plate in my Celestron C8 is way thinner than the meniscus lens of the 180mm Mak, which means the tube cools down a lot faster (but also dews up faster, so dew bands are often needed). It also means the OTA is much lighter which is nice when setting up, and requires less from the performance of your mount. This is Jupiter with the C8

This is with the 80mm

[dweller25]

For the planets you need good seeing, good aperture, good optics and good cool down as you will be at fairly high magnifications.

Sadly there is nothing you can do about the seeing.

Having tried many scope designs over the years there are two that to me stand out as the most suitable.

1. 8” F/6 Newtonian - not too heavy, rear fan to quickly cool the optics, cost effective, no dewing up, good resolution.

2. 120mm refractor doublet, fairly light, quick to cool, relatively expensive, will need an extra dew shield, pin sharp.

Hope that helps.

[Charlie 2436]

Thanks for the advice guys, it gives me a bit of thinking to do. I like the sound of the classical cassegrain, I’m not sure about the newt “collimation etc”. But at least I know that the 80mm f15 is not what I’m looking for. One last thing how do you think a 152 f6 achro refractor would be for the planets .

thanks Robert 

[johninderby]

A 152 f6 achro refractor would be good for low power wide field observing  (DSOs) but not that good on lunar / planetary where you would be using higher magnification. 

The chromatic abertaion that the fast achro would have at higher magnification on planeta also reduces contrast which is really important for good planetary views.

Edited March 30, 2021 by johninderby

[Alfian]

At one point I had both Mak127 and a SW 100ED. Foolishly I never tried them side by side. So much depends on seeing that I cannot clinically say that one was better than the other in terms of revealing a particular lunar feature. However my overall impression was that there was little to choose other than the fact that I found the ED100 gave an image that was more pleasing and involving to the eye (not necessarily any more revealing) even though the 127 had more aperture.  Interestingly my Tal100r (F10) even though it shows some CA is a wonderful lunar scope and my Vixen 80mm (11.4) is a cracker. Pre lockdown I came very close  to buying an OO 150 f8 reflector (several events conspired against this) and I was really intrigued to find out how different (better?) this would work out as larger aperture should in theory yield better resolution. It still might happen one day. Getting back to the Mak 127 though, given how easy they are to mount and use, and cool down isn't so bad, they are a very good scope for the money and to get something significantly better would involve a sizeable layout of cash.

[kirkster501]

The simple answer is that SCTs are the best scopes for the planets and the moon.  There is a reason why the megagods of planet imaging like Damian Peach and others use them.  Their long FL and large objectvies per £ make them ideal for planets.

[johninderby]

Had a C8 SCT but prefer the CC8”  for lunar planetary. Images are sharper.

[Basementboy]

3 hours ago, dweller25 said:

2. 120mm refractor doublet, fairly light, quick to cool, relatively expensive, will need an extra dew shield, pin sharp.

David, do you mind if I ask in your experience what you think is the best-value example of a telescope like this one? Ie highest quality balanced against lowest price? I have been looking at the Altair Ascent 102ED F7 doublet and wondering if there is a similar scope (F7 or relatively fast) that's got a 120mm aperture but isn't 1 meter long ... 

[Charlie 2436]

Thanks for the advice guys you’ve given me plenty to mull over. But I’m leaning towards the cc8 or the SW 180mak as I’ve read good reports on it the cool down isn’t much of a problem I keep my gear in the garage, like everyone I just want to get the right scope for the job within my budget.

thanks Robert 

[johninderby]

Skymax180s come up for sale second hand quite often so you might be able to pick one up at a good price. Classical Cassegrain 8” though never seem to come up for sale second hand.

[dweller25]

1 hour ago, Basementboy said:

David, do you mind if I ask in your experience what you think is the best-value example of a telescope like this one? Ie highest quality balanced against lowest price? I have been looking at the Altair Ascent 102ED F7 doublet and wondering if there is a similar scope (F7 or relatively fast) that's got a 120mm aperture but isn't 1 meter long ... 

Don’t want to hijack the OP’s thread, but you may want to ask @johninderby about this....

 

https://www.teleskop-express.de/shop/product_info.php/info/p10133_TS-Optics-Doublet-SD-APO-125mm-f-7-8---FPL-53---Lanthan-objective.html

Or this....

https://www.teleskop-express.de/shop/product_info.php/info/p4688_TS-Optics-Optics-120-mm-f-7-5-FPL53-Apo-Refractor-with-3--Focuser.html

 

Edited March 30, 2021 by dweller25

[johninderby]

Got mine from Astrograph.

https://astrograph.net/epages/www_astrograph_net.sf/en_GB/?ObjectPath=/Shops/www_astrograph_net/Products/AGTEC125F78

[neil phillips]

Personally i reckon This Sky-Watcher Explorer 150PL OTA | First Light Optics  would give the big Maks a run for there money. My 4.5 F8 Newtonian produces very very, pin sharp lunar images. I had two F15 Full apeture (8.25 oversized primary) 180 meade Maks Apart from focal length which isnt a problem, as barlows can close the gap

The above scope might even be sharper than Maks. Dont underestimate F8 Newtonians

[Stu1smartcookie]

12 hours ago, johninderby said:

The big advantage of the Classical Cassegrain is no corrector plate on the front. The CC will cool down in about half an hpur whereas the 180 mak will require a few hours. Also no dewing problems.The CC has a fixed primary mirror unlike the mak so no mirror movement. Also having a proper dual speed  crayford focuser makes a huge difference in focusing. I did upgrade the stock crayford with a Baader Steeltrack though.

The first photo is with the Scopetech f15 and the second is with the StellaMira f10.

Photo comparing the size of the 180 mak and the CC8” plus photos of my CC8” which is the TS version but identical to the StellaLyra except for the colour.

 

 

I owned a 180 Mak in a previous life ... have to say it is somewhat dwarfed next to the CC8... and i thought the Mak was big!!!

[johninderby]

Not much difference in weight though.

[Stu1smartcookie]

Just now, johninderby said:

Not much difference in weight though.

I like the look of the StellaLyra classical cass scopes . F12 (FLO) 6" version ... quite reasonable  price too .   

[johninderby]

1 minute ago, Stu1smartcookie said:

I like the look of the StellaLyra classical cass scopes . F12 (FLO) 6" version ... quite reasonable  price too .   

A very nice scope indeed although a bit on the heavy side. Over 6kg. Sold mine to help pay for the Tecnosky 125.

[Stu1smartcookie]

1 minute ago, johninderby said:

A very nice scope indeed although a bit on the heavy side. Over 6kg. Sold mine to help pay for the Tecnosky 125.

not wishing to hijack this thread , was there any collimation issues with a classic cass 

[johninderby]

No they hold collimation very well. Thr CC6” I had arrived in perfect collimation and when I shipped it to another SGL member it was still perfectly collimated when they checked it.

I played around with the CC8”” collimation but that was just to find out how to collimate one as it didn’t need collimating.  That was a year ago and hasn’t needed collimating since.

Think they might only need collimated if knocked about in shipping.

Edited March 30, 2021 by johninderby