Mak frustrations!

[Guest recceranger]

I had great clear skies last night and gave the Mak a run out.  Report below!

 

Ok, after all my who ha about my new Mak 180 pro I finally got it out tonight for a full first light test. While waiting for the moon and Jupiter to come into my FoV I targeted Rigel, some of M45 and the Orion Neb. 

 

On adjusting focus on Rigel I couldn't get that razor sharp focus that I can with my ED80. In fact no where near. So I tried another few bright stars higher up from horizon including some of M45. Again focus wasn't at all what I expected. I have heard so much about the mak and how it's very near to an APO so I was a little surprised. At the start of the session (and it was very frosty!) for a period of around 10 - 15 mins I realised I had forgotten the dew shield. Perhaps this was the cause for lack of focus.

 

As soon as Jupiter came online I locked on. First impression was disappointing as once again I couldn't quite get that sharp focus and the legendary Mak contrast was nowhere near my ED80. This was on the 24mm Baader Hyperion so I tried my SW Click stop zoom. As soon as I went below 18mm all contrast was lost! Not exactly killing planets!

 

On observing the moon all was well at low mag i.e. 28 - 24mm but on increasing power again contrast left the building.

 

I must say that I was really looking forward to getting the Mak out as the reviews are fantastic but it's not the experience I'm having. My Q is could all this be as a result of initially not using the dew shield? Or would it be an issue with the scope?

 

I have looked long and hard at the primary lens and mirror and can see nothing wrong. However, other Mak users are posting great images using Barlow lens etc. when I tried a Barlow contrast disappeared!

 

Can anyone for a little advice as £700 odd quid doesn't grow on trees!

 

Rick

[Perkil8r]

There are a few things to consider.

 

Did you allow time for it to cool? Maks tend to take a fair while to cool, this can make a big difference to the quality and clarity of the image you obtain. For example I allow the 16" at work 3 hours to cool, and that has a fan to help!

 

Was there any dew on the objective or correction plate? (that's the big plate of glass at the "skyward" end of the scope.

 

Had the eye piece misted over with dew?

 

Both of those are easy to sort with either a dew shield or dew bands.

 

Lastly, on the next occasion you get, centre on a brightish star. Get somewhere near focus then knock it out of focus in an inward direction. What you are aiming to do is get a shadow of the secondary mirror on the middle of the out of focus star. It should look a bit like frog spawn. If that shadow is not bang in the middle of the star then your scope probably needs collimating. This is not unusual nor is it an expensive issue. It's just some adjustment of the mirrors that you can do yourself with a little direction and patience.

[Brantuk]

Did the meniscus lens look like it had any dew on it Rick? I guess you would have noticed if the eyepiece or finder were dewed up. However it's possible there may have been some dew on the optics inside of the tube - less noticable - and it was quite moist in the air last night.

 

Dew would also have limited magnification a fair bit - reducing contrast further especially at higher powers. Did you use any form of dew control at all, apart from a dew shield?

[Guest recceranger]

Thanks guys,

 

Mike, I did check the off focus test and noticed the central circle was just slightly off centre when brought out of focus but I didn't know if this would cause loss of contrast.  Is there a point of contact were I can get advice on how to adjust.  Warning! I'm a buffoon with fiddly bits, Lol.

 

Kim,

 

Just a dew shield and didn't apply until I remembered 15mins into session.  Everything was soaking last night so I guess I was kicking my own butt!  

 

As for cool down I had it out for around 3hrs and it didn't seem to improve.  My ED80 was crystal clear by comparison.

 

Thanks for the response and hopefully I get another chance over the next few nights to take a look (with dew shield on from start!)

 

Rick

[Perkil8r]

If it was only slightly off it's not likely to have been enough to disappoint. I would say the issue is more than likely dew related.

[xanthic]

Conditions at my home were 1 degree C with 95% humidity. If it was anywhere similar, I can't imagine it not having dewed up. It was a show stopper for me setting up.

[philjay]

I have a 180 Mak and fidnt even think of taking mine out last night for lunar and jup, why because conditions were only good for low mag

Youve experienced what every new mak owner experiences at some time or other, crap seeing which allows only low mag views.

The rules of using a mak for planetary are

cool down

dew control

atmospherics

last night the jet stream was part over us and even with no wind at ground level the high altitude wind makes higher mag planetary viewing a waste of time.

An f15 scope needs getting used to, i have the same scope as yours plus 2 other f15s so i am used to it. Dew on the corrector will be obvious, you do need a dew shield for these scopes in the uk, its a fact of life im afraid. If you had the scope cooling for 3 hours then once the caps off dew will form rapidly on the corrector, this will be obvious by just looking at it and if its dripping wet then you have dew problems.

Dont even think about adjusting collimation it wasnt that also, you havent wasted your money you have just got a bit of a learning curve im afraid

[xanthic]

I've already posted this in it's own thread, but here is the real time wind map. The link is set to show the jet stream over the Atlantic and UK at present.

 

http://earth.nullschool.net/#current/wind/isobaric/250hPa/orthographic=-23.52,53.01,1107

[Guest recceranger]

Thanks guys,

 

Sound advice.  Wasn't aware about the atmospherics and cheers for the link.  I live and learn! 

 

To recap, I assume the main suspects are dew/atmospherics and probable nothing to do with collimations issues.  This twined with the fact I'm a Mak raw recruit! 1st lesson learnt and already discovered I need a focuser upgrade but this can wait until new year!

 

Rick

[Perkil8r]

Yes, Collimation sounds close from what you say, so that will be the final tweak once everything else falls into perfect harmony

[philjay]

These Maks are built like tanks and nothing short of severe trauma or a previous owner that doesn't know what they are doing will put them out. So for the moment forget about collimation being your problem, ( maks are not like newts where collimation is a regular thing).

 

Then once you are happy with everything else dew control, atmospherics etc bring it to a meet so I can take a look at what issues you have.

You only star test these on the best of nights then at different mags and you must have the test star in the centre of the scope, if its to one side it will give the impression of being out. So by the very nature of the seeing being crap last night your start test cannot be relied upon

 

 

I would also recommend giving it awhile before splashing out on a new focuser, for visual I think the standard is basic but functional I do however have a motorised Crayford on mine which I use only for imaging.

[catman161]

Sorry you had problems rick. I stuk my head out the back door and saw it was clear. Went out for a few minutes just looking and decided not to set up as it was so humid. Plus I would have liked I image Jupiter and it was almost directly above the moon.

[Guest recceranger]

Guys,

 

Thanks.  It appears its more my lack of knowledge than anything else.  I have now calmed down and took stock! Will have another bash on a better night (hopefully this side Christmas)

 

On another point, why the hell didn't I get an HEQ6!

[andyboy1970]

Have you tried the scope in daytime?

Silly question ---- Did you use a diagonal?

[Brantuk]

If my Sct corrector is anything to go by then the Mak meniscus will be a right dew magnet. I've not had my Mak out yet but when I do it'll have a dew band on the front and a dew shield. It'll also be cooling in the garage all day before use.

 

The interesting property about Maks is their long focal length which gives really tight focus on planets almost like a refractor. Unfortunately this wonderful property is their downfall in poor conditions cos it will focus nicely on any atmospheric imperfections at the same time - even more so at high magnification. So judging conditions can be critical.

[+Ibbo]

My advice is if the stars are twinkling like mad don't bother with the long focal length scopes or high magnifications.

 

Transparency was good here last night(ie nice and clear) but the seeing was awful(stars twinkling like mad)

 

The best planetary observing and imaging conditions I have had are is when the atmosphere is still, in fact its was a poor night for deep sky as transparency was poor almost misty.

 

Steve