a visual comparison 10" f15 mak v 12" f 5 dob

[stuy]

this is just a purely a visual evaluation of these scopes taken this week under good seeing using saturn as a target, first up was the dob which was made for me by david jackson in norfolk, using a very good primary which was made in russia!! the scope was allowed to cool as with all of the other scopes . the seeing was 6-7 pickering

SATURN IN THE 12"DOB

using a tracking platform was straight from the off really good very sharp, using a pentax eyepiece @ 240x cassini right around the planet shadow very defined and some good details on the planet banding etc.. this was going to be a close call.

SATURN 10" F15 MAK CASS (intes micro)

so having invested a heap of cash in this scope i was a bit concerned after the image the dob gave, so using another pentax using 250x the first impressions were not great !! but the scope needed more time to cool down!! this is the only downside of these fine scopes they have a lot of glass!! but i had all 3 fans working 2 across primary 1 at rear, soon reached ambient temp then it really showed its class the contrast was a lot better than the dob, i kept going back and forth to the dob to check it also , of course the dob had a brighter image,

and yes there was a marked difference in contrast and the color looked for me better in the mak cass , the cassini looked really black and the polar region of the planet looked nice and dark but could not make out the the hexagon!! the banding across the globe looked also more defined!!

so after this purely visual comparison was the investment worth it?

well for me it does seem like , but these big maks ONLY come into there own when we get really good seeing , which as we all know is so seldom here in the uk .but when we get the seeing they will not let you down, for all there problems with cool down times etc... they are a worthwhile investment if you like me want the best image possible regards stuy

[oldfruit]

Interesting comparison. I have observed the same with Jupiter. I used my 12 inch dob and compared the view through a friends Celestron 9.25. Even though the dob gave a good and brighter image, the 9.25 showed a little more detail and the contrast was much better than in the dob. I would go so far as to say that the detail was visible in both scopes but was far more obvious in the 9.25.If someone wanted a great scope for planetary then the Mak would be the way to go. It was not too shabby on dso`s either.

[stuy]

Interesting comparison. I have observed the same with Jupiter. I used my 12 inch dob and compared the view through a friends Celestron 9.25. Even though the dob gave a good and brighter image, the 9.25 showed a little more detail and the contrast was much better than in the dob. I would go so far as to say that the detail was visible in both scopes but was far more obvious in the 9.25.If someone wanted a great scope for planetary then the Mak would be the way to go. It was not too shabby on dso`s either.

yes the finer detail was alot easier in the mak cass, i will now make a comparison with the 10" mak newt should be intresting regards stuy

[John]

Interesting comparison Stuy

Out of interest how do the costs of the two scopes compare ?

For planetary viewing my 12" Orion Optics dob seems to start at 267x and then I can go to 318x or even higher if the conditions allow.

Those Intes mak-cass's sure pack a punch though. The largest I've used was a 7" - the 10" must be a really fine instrument

[umadog]

I've got to say, I'm surprised the contrast is better in an Mak given the 33% obstruction. What do you think accounts for the difference? Better optics in the Mak? Exit pupil differences? Better baffling?

[stuy]

I've got to say, I'm surprised the contrast is better in an Mak given the 33% obstruction. What do you think accounts for the difference? Better optics in the Mak? Exit pupil differences? Better baffling?

well the 10" f15 has a obstruction of 26%!!! the standard f 10 has 33% but the f15 is a super planetary version made to order, and as you say the baffling and the very good optics !! must account for this but as i said it was a close run thing indeed!!! i am trying the mak newt tonight we shall see what it does regards all stuy

[stuy]

Interesting comparison Stuy

Out of interest how do the costs of the two scopes compare ?

For planetary viewing my 12" Orion Optics dob seems to start at 267x and then I can go to 318x or even higher if the conditions allow.

Those Intes mak-cass's sure pack a punch though. The largest I've used was a 7" - the 10" must be a really fine instrument

hi john ! well there is a big difference with the price!! the dob cost 3000 pound and the and the two maks are 9000 grand apiece!! stuy

[F15Rules]

Fascinating comparison Stuy :-)

I have done a comparison with my Intes M603 fully cooled and a 6" Celestron refractor F8..although the Celestron will show slightly more faint stars, the contrast in the Mak is much better, and I'm sure it;s the baffling. In fact I've never seen better contrast, ie dark sky background in another scope. Even the dewshield is fully baffled!

I agree that the Mak's only give of their best in the best conditions, so for average nights the difference between my £1300 new cost Mak and the £550 new cost Celestron OTA is not easy to see, and on some views, eg widefield, the Celestron actually has the edge. But there is something about the quality of these Maks that just draws you in. And I say that as a refractor fan first and foremost.

But £9k for an OTA.... :eek: ...you're then into Zeiss/AP/Lomo TMB etc big frac territory!

cheers

Dave

[umadog]

Ah, a 26% obstruction... That should help, I'd I think. Also, the lack of the diffraction spikes makes the view more pleasing. It definitely gives the impression of a darker sky background.

I agree that the Mak's only give of their best in the best conditions,

Can't you say that about any scope, though? Why is it especially true of a (larger?) Mak?

But £9k for an OTA.... :eek: ...you're then into Zeiss/AP/Lomo TMB etc big frac territory!

Yeah, but you won't get a 10" frac for £9k, though!

[omahaastro]

Meh... they can keep their expensive glass.

[nicks90]

is the better contrast also down to the speed of the scope? a 12" dob will be quite fast - F4.5-F5 ish - whereas the mak was an F15.

How would that influence the performance with the given eyepieces and general observing quality?

[stuy]

is the better contrast also down to the speed of the scope? a 12" dob will be quite fast - F4.5-F5 ish - whereas the mak was an F15.

How would that influence the performance with the given eyepieces and general observing quality?

the f ratio wont really affect the visual observation s nick it just helps with the longer focal ratio to use eyepieces with better eye relief (20mm etc..) than using a barlow in conjuction with say a 10mm etc.. i think its probably down to superb baffling and very smooth corrected optics of the highest order, regards stuy

[omahaastro]

The Newt benefits from an AFV of over 1 1/2°... the Mak provides little more than 2/3rds of a degree.

[Stu]

Umadog, I have never understood the technical explanation, but as the owner of an 8" mak (f20), I would concur that they are fickle beasts! They seem to be sensitive to seeing conditions and do need things to be right to give their best performance. When they do they are fantastic though.

Stu

[stuy]

The Newt benefits from an AFV of over 1 1/2°... the Mak provides little more than 2/3rds of a degree.

very correct indeed omahaastro but really as a visual planetary observer the limited fov for me is not an issue, as i said it was very close, but since the post last week been using the 10" mak newt and think that has a slight edge over the mak cass!!!! we are talking very slight but it looked better, of course could of been the seeing havent got a mount to do the big maks together thats whats needed regards stuy

[Dunkster]

My question is... why would an improvement in contrast and colour rendition only be useful with good seeing? Surely the benefits are just as useful at lower magnifications too

[Stu]

Dunkster, with maks in particular, low magnification isn't necessarily possible!

Mine is more extreme at f20 and a 32mm Plossl gives me a low power of x125 with under half a degree fov! I guess that answers the question of why they are more sensitive to seeing, because its not easy to back off the power when the conditions aren't great.

Stu

[alan potts]

Stu,

Yes they sure make even the longest F/L eyepieces give high magnification and I am only talking about the baby 180mm, it is the same for the Meade though so I am used to it. I have to say in the limited time I have used it it gives better images than the F10 meade, bear in mind it it a fair bit bigger too.

Alan

[Stu]

Yes, it's weird using a 21mm ethos as a high power planetary ep giving x190!

I've recently acquired a few more Plossls giving in the x125 to x267 range. I figured that there is little point using my 2" wide field eyepieces, and at f20 the Plossl should be fine. Hopefully they will give lovely sharp images with minimum light scatter and great sharpness. I say 'should', because I've not yet had a chance to try them out.

Stu

[nicks90]

question from the cheap seats at the back

with these super long focal length scopes - if you put in a x0.5 focal reducer, obviously this would half the magnification of each ep you use. But would it also increase your field of view, or is that set due to the physical focal length of the scope before the focal reducer does its thing at the ep?

[Dunkster]

Sounds like those big Maks need one of these ... http://www.optcorp.com/explore-scientific-30m-100-degree-3-argon-purged-eyepiece.html

I use my 17mm Ethos with my C11 (f/l _only_ 2800mm!) and it's a cracker

[Stu]

Those 3" eps are a bit crazy aren't they! Would love a look through one, though most scopes would need a severe focuser upgrade to take one. Can't quite see a market in hybrid 2" to 3" diagonals!!

Regarding focal reducers, I do have a x0.5 around somewhere which I will try at some point, but not sure if it would work or not. In general I've given up trying to fight against the narrow fov on mine and use it for what I bought it for ie lunar, planetary and small/bright DSO's which it excels at. The Plossls should maximize light throughput and give a nice punchy image.

To Michael's comment re image shift on maks/SCTs, I can only say that Orion Optics did a superb job with the OMC200 focusing. It uses a micrometer type adjustment wheel and there is absolutely zero image shift even at x400 or more. Having said that, it's pretty essential when the fov is only just over 0.1 degree! You'd never keep anything in view otherwise.

Stu

[alan potts]

Nick,

To answer your question yes the FOV is increased, I sometimes use one on the LX 200 and can get a FOV of about 1 degree using an .63 reducer and a 26mm eyepiece. Doing things this way gives you the maximum FOV. I believe I can use the same on the Maksutov but I need a thread adapter and they don't seem so easy to lay hands on. Having said that though I got the Mak for planetry so not really nesessary, the thread converter is more for putting a better visual back on the scope.

Stu,

I think these massive eyepieces are only going to give the type of scopes we have problems. I don't feel that even my 12 inch is strong enough to handle one. I would say that the 14 inch LX or even better the 16 inch are nearer the mark and the latter few people own. I mean even if it were balanced think what it is doing to the motors. I think this is an eyepiece really for the big scopes, sort of 18 inch plus area.

Alan.

[Dunkster]

The 30/100 should be OK on the LX Alan, the rear cell of SCTs is cast in iron/steel, so the cell thread should be pretty strong. After all, people hang additional focusers, filter wheels, OAG and DSLR/CCD cameras off the back

Whether it's so useful on a Mak is another question. Whether there'd be any gain would depend on the baffle tube diameter which I expect - along with the smaller secondary - is narrower than the larger SCTs...iirc it's 54mm in diameter on the C11, so plenty of room to go over what 2" EPs can accomodate

[alan potts]

Dunk,

We will see, if I ever get the adapter for the threads. I have the .63 reducer from the Meade, I am told they do the same job and one being F15 and the other F10 makes no difference. As for the 30mm eyepiece I don't think I will be trying one out, I just think it's will be too much, if it were to have uprated motors maybe. Try it on yours and let me know.

Alan.