Skymax or Astromaster 90

[Mike_S]

Hi,

Sorry a shorter but briefer post after a couple of weeks studying all the options for my first scope and changing my mind multiple times I finally today felt ready to order a Celestron 90mm F11.11 achro EQ for £169 plus some additional eyepieces and filters. I’ve realised that I want something very quick to set up so that I use it often. This is for planetary and lunar visual not AP. 

However, I keep reading about Mak’s or SCT’s being great for viewing planets.

Thing is the area I am in apparently you can only expect useful magnification of 10-12 x objective which I can easily achieve with this achro and say an 8mm eyepiece or a Barlow. 

I could also achieve this with a SkyWatcher Skymax 90 EQ1 for £163. 

Ive been playing about with the Sky at Night field of view calculator and it seems to be about the same. 

I like the sound of the F11.11 refractor because this should have minimal chromatic abberation. It meets the sidgwick standard of a focul ratio 3 x the dismater in inches. 

With a Mak I may have to collimate but hardly ever? I have heard the achro should have better contrast? Or maybe the Mak would give a sharper image? Really not sure what the difference is going to be besides the size. 

I have also been advised that the Celestron mounts are slightly better at this price range?

so what is better for planetary viewing and why? 

[nightfisher]

The astromaster mount may be a tiny bit better, but with a long frac on it there will be a fair amount of wobble, where as the EQ1 with a 90mm mak on it should be very stable, i would put my money on the Mak, you should never have to collimate the mak unless it gets dropped on concrete

[Alfian]

If you are mainly interested in Luna/planetary observation then the little Mak would be my choice. The refractor will give better contrast but more CA and a slightly wider field of view.. The Mak will not show CA and will have slightly less contrast. The Mak by the way will not give a full 90mm aperture but I doubt whether the difference side by side would be overwhelmingly obvious. The  mounts for me would be an issue. The Celestron CG3 mount is in reality more akin to an EQ2 (I used to have a Celestron 130EQ -CG3) and as Jules has said I think the long OTA of the Celestron would be frustratingly wobbly - having to wait a few seconds for it to settle down every time you touch it., particularly so at higher magnifications. I think its interesting that the Skywatcher Evostar 90 (which I would prefer over the Celestron in terms of a 90mm achromat) is offered not only on the EQ2 but significantly also the EQ3, I wonder why? The EQ3 is a far better mount. Having said that I would not be that fussed about the EQ1 either, the Mak 90 is light and the EQ1 is probably adequate but I would prefer the simplicity and more intuitive qualities of an Altaz mount. Unfortunately the Mak90 isn't sold with one as far as I'm aware and buying the scope and mount separately would bump the budget up, but you could still go for the Mak90/EQ1 and look around for a second hand Altaz (AZ3/)? An interesting review (see link) on the Starmax90 which is all but the same as the Skymax90.

https://www.cloudynights.com/articles/cat/user-reviews/telescopes/maksutov-cassegrains-mcts/starmax-90mm-eq-r763

[happy-kat]

I thought you were avoiding eq mounts and the 90mm achro is available on an altaz mount with slo mo az3 Skywatcher evostar 90mm.

[happy-kat]

Though the size and portability of the skymax 90 is great. Can always as suggested look it for a second hand mount or use a sturdy photo tripod based solution.

[Mike_S]

Yes I had a telephone conversation with a friend who recommended an EQ mount because of how quickly the planets move out of view. I have been considering the Evostar 90 as well. I’ll have another look a these mounts, thanks. It is concerning that the Evostar 90 also comes on an EQ3-2 mount. Hmm.

[Mike_S]

I could also add the motor drive for the Celestron mount to reduce the vibrations. 

[Alfian]

26 minutes ago, MSammon said:

Yes I had a telephone conversation with a friend who recommended an EQ mount because of how quickly the planets move out of view. I have been considering the Evostar 90 as well. I’ll have another look a these mounts, thanks. It is concerning that the Evostar 90 also comes on an EQ3-2 mount. Hmm.

Once you pump up the magnification objects do move through the field of view quickly. Its completely logical but it still surprised me when I first set out!  Equatorial mounts are useful in this respect in as much that once polar aligned and setup it is easy to track objects. The down side is that at times it can be awkward and I read somewhere someone speaking of the "equatorial dance" which you kind of learn. Altaz mounts are much more intuitive to use and TBH, assuming a mount has slomos you are just tweaking two controls as opposed to one, ignoring motor drives of course. The Giro altaz I have has no slomos but is very smooth and you just gently steer dob fashion. In terms of the Evostar EQ3, its not that the EQ2 is a disaster but that the EQ3 is a sturdier more substantial mount that just works better. 

[Mike_S]

I think due to cost and I’ve read a lot of good reviews about the Astromaster 90EQ I think I’m willing to give it a go. I just watched some set up videos on YouTube. People were saying they only take a few minutes to set up but it seems to take a good 5 minutes. Do they come with a case to store them? Do people strip down their EQ mounts every time?

[Mike_S]

Another thing I’m thinking is if i don’t try this F11 90mm refractor then I might never try one as when the budget goes up then achromats fall out of favour and I won’t know if it’s worth getting an Apo. Though the mak is still appealing as long as I can fit a 32mm eyepiece to it for finding.

[Alien 13]

I am someone who thinks the Mak is a keep forever type of scope even if you add others over the years, It is so good for grab and go and makes a good camera lens too..

Alan

 

[Mike_S]

I think I’m definitely going for an EQ mount. So I’ll let you know what I decide over these two. Handy on the Skymax 90 that it’s so short so easier to use rather than the eyepiece being at the end of a 1000 long scope but I still prefer the sound of the view out of the refractor. Shame I can’t really try any. I’m going to an astronomy club tomorrow so will see. 

[RT65CB-SWL]

The reasons I favour catadiopric 'scopes over long refractors is...

1. compact storage/space saver when not in use.
2. easy to transport if reliant on public transport.
3. can be 'easily' attached to most mounts by one person.
4. no tube flexure if tube rings are used on a short dovetail bar or due to wind blasts.
5. storage cases are readily available.
6. can be used for terrestrial observing.
7. the image is the 'right-way' up.

The only downside is...

1. the cool down time. Anything from 30-60+ minutes.
2. a dewshield and/or star diagonal are 'must have' accessories.
3. not all have a 'standard' SCT threaded port for third-party accessories.

 

...and my favorite ---> 

[Mike_S]

Just been to an astronomy society. They reckoned the mak would be better for planetary viewing as they said I will still get the colour abberation on an F11 90mm Achro. But people say the contrast is better on an  Achro. Would you say CA even on an F11 90mm would be a worse view than the lack of contrast on a maksutov of the same aperture?

[dweller25]

I have had both Maks and Achromat refractors - for the planets I prefer Maks as I do not like chromatic aberration.

I would say the contrast in a 4" Mak is as good as in a 3" Achro.

Maks are more comfortable to use than Refractors as they are physically shorter and because of this the Mak will be more stable when focussing.

Maks take longer than Refractors to cool down - but if you wrap them in silver thermal material from B&Q they are good to go straight away.

My suggestion to you is to go for the Mak - but try to stretch to the 127mm.

 

BUT just to throw you a curved ball - a 6" F/8 Dobsonian will show much more detail than the scopes you are thinking about....

https://www.firstlightoptics.com/dobsonians/skywatcher-skyliner-150p-dobsonian.html

AND It's quite easy to manually follow a planet especially if you buy a wide-ish angle eyepiece like this ...

https://www.firstlightoptics.com/bst-starguider-eyepieces/bst-starguider-60-8mm-ed-eyepiece.html

AND it can be put on an equatorial mount at a later date.

 

[Mike_S]

Thanks the guy at the astronomy club suggested a 127 mak too. Have been considering a dob but not sure about storing it yet as my shed is full of new kitchen stuff. Maybe when the kitchen is done i’ll get something bigger. 

[Mike_S]

Thing is it seems people recommend spending a bit more on a slightly bigger mak but I just want a starter scope and a 90mm refractor will gather more light than a 90mm mak. It’s only about £6 more for the 90mm refractor but £85 more for the 102mm mak. I think with the cool down time as well I’m going to try the refractor. If the CA or the size of it annoying I can replace it.

[SIDO]

On planets a 90mak and a 90 f11 achro will be the same on detail the difference will become very clear though on a target like Orion, the 90 f11 will show more hands down. So field curvature with mak chromatic aberration with the achro but brighter and more detailed dso where the ca matters little. I had both and this has been my experience.

[RobertI]

Another important point I think is that breezes will affect the frac much more than the mak because if its length, you may actually get more useable observing time out of the mak.

[Mike_S]

Yea good points. I think for a first scope it’s got to be quick to set up. I think I’m going to order this today. When I want better I can always get a 127 mak or something for planetary for an 8 or 10 inch dob for deep space. 

[rwilkey]

On 08/08/2018 at 02:40, MSammon said:

you can only expect useful magnification of 10-12 x objective

The maximum useful magnification of any telescope is approx. twice the objective depending on sky conditions etc, the usual maximum suggested for the UK is 200x, though more can be acheived with a better and bigger scope.  Don't get hung up on magnification, most stargazing is done at lower magnifications

[Louis D]

On 08/08/2018 at 06:59, Philip R said:

The reasons I favour catadiopric 'scopes over long refractors is...

1. compact storage/space saver when not in use.
2. easy to transport if reliant on public transport.
3. can be 'easily' attached to most mounts by one person.
4. no tube flexure if tube rings are used on a short dovetail bar or due to wind blasts.
5. storage cases are readily available.
6. can be used for terrestrial observing.
7. the image is the 'right-way' up.

The only downside is...

1. the cool down time. Anything from 30-60+ minutes.
2. a dewshield and/or star diagonal are 'must have' accessories.
3. not all have a 'standard' SCT threaded port for third-party accessories.

 

...and my favorite ---> 

More upsides over Newts and some refractors:

1. Have ample back focus to allow for prime focus imaging, filter wheels, and binoviewing without additional optical aids.
2. In general, hold collimation better than Newts, but not as well as refractors.

More downsides over Newts and refractors (especially fast EDs and APOs):

1. Can have mirror flop during back and forth focusing.  It isn't present on all CATs, but many do have it.
2. Larger central obstructions for a given aperture relative to Newtonians to enable the light path folding leading to decreased contrast.  The faster the focal ratio, the bigger the obstruction just as in a Newtonian, but the CO is much bigger at a given f-ratio.  Refractors have no CO at all.
3. Limited wide field viewing possibilities due to the typically long focal ratios due to the slow focal ratios.  An f/15 Mak will show 1/9th as much sky by area as an f/5 Newt of equal aperture, yet both have the same maximum theoretical power.  Even here, the Newt will win out with the smaller CO yielding tighter images at high powers.  As such, it is almost a must to pair a Mak or SCT with a short ED or APO refractor for wide field views if you enjoy viewing a variety of targets.

Neither up nor down side:

1. The image is "right-way" up only with the use of a diagonal, the same as a refractor.  However, it is reversed left to right unless an Amici prism diagonal is used.  Perhaps you were comparing to a Newt?

[SIDO]

On 10/08/2018 at 08:12, MSammon said:

Yea good points. I think for a first scope it’s got to be quick to set up. I think I’m going to order this today. When I want better I can always get a 127 mak or something for planetary for an 8 or 10 inch dob for deep space. 

Cool that you are learning more and maybe getting on with your choice of a telescope, if it is the 127mm than its a good choice and down the road when you get that larger heavier deep sky scope the 127mm will be a nice alternative to lugging out the big scope when conditions, moonglow or the days physical stress warrent a less is more approach. Be sure to post your first light observations with us, would be great to hear your experiences with the new scope ?

[cletrac1922]

On ‎10‎/‎08‎/‎2018 at 07:22, MSammon said:

Thanks the guy at the astronomy club suggested a 127 mak too. Have been considering a dob but not sure about storing it yet as my shed is full of new kitchen stuff. Maybe when the kitchen is done i’ll get something bigger. 

Dob is great for viewing planets and other DSO's

Disadvantage of dob, does not track

When comes to Equatorial mounts, now able to get an Wi-Fi adaptor, and takes all the guess work out of setting up a HEQ5 or 6

Recently purchased one, and downloaded the APP

The beauty of the APP, once done 2 star alignment, just point your mobile device where to observe, and select object, and mount goes straight to it