Altair Astro Wave Series - 80mm Triplot Apochromat Refractor

[badgers]

I think pretty much all refractors need a flattener for astrophotography, some of the super-expensive refractors have the flattener built in though.

Reducer is for a faster wider-field, but to be honest I'm very happy with it as it stands.

Anton

[badgers]

Well I should clarify... A flattener isn't essential, but it would be fairly counter-productive to buy a £700 telescope and not correct the field.

[michael.h.f.wilkinson]

Visually I do not use a flattener in most cases, as the eye can handle slight field curvature quite well. In a few occasions I have used it, but getting the spacing right is not trivial. I will use it for imaging (come the day). I do not use a finder scope with this little scope, as it has a 5.3 deg FOV with the 31mm T5. I generally find things quite easily

[kirkster501]

Why is this spacing so important? And how is it achieved on this scope? What spacers are required

Sorry if I am going off topic of Anton's review.

Steve

[ollypenrice]

Hi Anton, thanks for your comments, most interesting.

Question though if I may? Why does a scope with such a superb image need a field flattener?

And why a reducer - to give a wider field?

Rgds, Steve

It's optically impossible to make a front element refractor with a large flat field and in visual use it isn't necessary. For a flat field you absolutely have to have a rear element. This means that front element doublets and triplets need rear end mounted field flatteners. The alternative, which has been around since the dawn of astrophotography, is to use the four element Petzval 'portrait lens' design and this is the top option. It has a front doublet and a rear doublet. Put your hand in your pocket (these things breeze onto the market at over £3000 for an 85mm) and you can have them from Takahashi and TeleVue. They not only offer huge flat fields and superb colour correction but also freedom from the need to respect a set chip distance. You just put in the camera and focus. Bliss.

Reducers do two things. They give a wider field and they speed up the F ratio and thereby reduce exposure times, or go deeper in the same time.

The best doublets and triplets in the world (Tak, TV, TEC, AP, TMB etc etc, all need flatteners for imaging but not for visual.

Olly

[kirkster501]

Thanks for the explanation Olly. So why the set distance for the flattener - and how do you achieve that distance? As with Antons setup here. He bought the field flattener but he mentions it has to be a set 52mm. How is that done? Some sort of extension?

Thanks, Steve

[michael.h.f.wilkinson]

In a Petzval system (as I gather it) the rear elements are at a predefined (correct) distance of the front. All the focuser does is put the imaging device or EP at the right point. In the case of a doublet or triplet with a flattener, the flattener is mounted into the focusing tube, so it moves with respect to the front element. Thus, the focuser is used to put both the flattener and the imaging device at the right point. To ensure that the flattener is at the optimal location when the image is in focus, you need to set the optimal distance between ccd chip and flattener first. My flattener came with a 2" diameter spacer which screws onto the flattener, and has a T-mount thread at the other end. as the t-mount has a predefined distance to the image plane, simply attaching a t-mount adaptor for your camera suffices (assuming you do not want to insert filter wheels and the like).

[billhinge]

Thanks for a great thread, just ordered my Altair Wave Series 80mm F6 Super ED Triplet APO , hopefully should have it for the weekend, not that I'll see anything

also ordered the optional tilt adjuster just in case

Got a milestone birthday in a couple of weeks, my excuse

[billhinge]

My new 80mm Astro Wave arrived yesterday, looks and feels wonderful. Unfortunately there was an issue with the flat field corrector so I'm waiting for a replacement.

Good job the 5 day weather forecast predicts cloud and rain, hopefully get some clear skies over the christmas holidays

In the meantime decided to look down the draw tube, it has a basic metal finish, ie doesn't appear black coated. I have some protostar flockboard left over from my sct flocking.

Do you think there would be any reason not to flock the inside of the draw tube (it seems to work beneficially on the inside of my sct)

By the way in case anyone is searching the forum in future, a little bird indicated that this is the same factory model as the TS TLAPO804 (I was trying to decide between these two),

Altair claim their Astro Wave to be the higher spec but regardless I decided to go with the UK seller

[billhinge]

Well, collective wisdom of my internet research says flock it, so I will

[badgers]

Yes the parts are the same, or at least come from the same factory. This is handy as I was able to order the Teleskop Express motor focuser and it fit directly.

I think the key difference is in the optics and how well the scope is put together. Mine is still delivering the goods between the clouds.

The TS motor focuser is absolutely fantastic. I used to focus by Bahtinov but in these cold nights, I'd find I'd have to refocus every hour or so until the temperature stabilised.

MaximDL will autofocus it on my Luminance filter in about 2 minutes and I've got offsets inbuilt for the RGB and narrowband filters.

I've not flocked the dew shield, it does appear to be blackened but I may flock it anyway I think I have some spare around the house somewhere.

[billhinge]

Thanks Badgers, never thought about getting a TS motor focuser, good tip but I think that will have to wait for the summer, not sure I can get away with anymore new toys for a few months

Just a quickie, do you find that you have to use a star diagonal to get focus using the eyepiece holder and eyepiece, ie without the flattener

[billhinge]

Seems to have increased in price by £100 , glad I bought it when I did. Just wish the weather would improve to let me use it

[badgers]

Sorry I missed this Billhinge. I normally use a diagonal, but I remember having to use a 2"-1.25" extension to get focus without the flattener. I guess it's designed with a diagonal in mind.

Don't mention the weather : (

[billhinge]

No problem Anton

In hindsight it was probably a dorky question, I normally use a SCT so back focus hasn't been a problem previously. After posting the question I subsequently read that modern refractors quite often require a couple of inches in between to focus.

I've now got the flattener back from Altair, everything is fine on terrestrial targets with eyepiece and camera, now just waiting on the weather. Nothing promising in the next 5 days weather forecast , hopefully will get some time before the end of the holidays

[petercoxphoto]

Thanks for the review Anton. This scope is at the top of my shortlist at the moment for AP use.

Cheers,

Peter

[billhinge]

For info

I was just buying the Altair 10x60mm finder from the Altair web site and came across this new Altair blog on the the different types of ED optical glass used (e.g. FPL-53) and and the quality of the Altair models eg this one

https://www.altairastro.com/xcms_entry.php?xcmsentryid=3&keep_https=yes

By the way I have no affiliation to Altair other than as a satisfied customer, just raised it since it seems a useful informative blog

[Mondlicht13]

Thats it then. Decision made.

This is the one for me

[billhinge]

I would recommend a finder and flattener as well, the Altair 60mm is nice if you can spring to it but I think you will like it

[Mondlicht13]

Thanks Billhinge.

Scope plus flattener arriving tomorrow

[badgers]

Looking forward to hearing some other people's experiences with this scope.

Actually, I'm more looking forward to clear skies and no moon.... but that hasn't happened for me in about 6 weeks : (

[Mondlicht13]

Hi Anton

First off thank you for the review you did on this scope. I'd done plenty of research before committing myself.

Your excellent review and comments by Billhinge above helped my decision.

Due to the awful weather, I've got serious wind today again, pardon me !! it's not seen First Light as yet.

Will certainly post my experiences with it weather permitting. At the minute Saturdays forecast looks favourable. Fingers crossed.

The build quality of the scope is excellent. It feels solid and looks as good as far more expensive instruments.

Will post again when I have something to report. Cheers for now. Hope we get those clear skies.

[kirkster501]

I keep considering this scope. Yes, a Tak woudl be ideal. But not sure I can justfy that much spend when I need a Carbon Fibre bike as well..... I have the same CCD as you too Anton. What's your thoughts now you've had the scope for a bit? What do others think?

Steve