DaveS

Well the Taks are designed as a piece, a Petzval quadruplet. All these six element astrographs are built from existing apo triplets with a supposedly matched three element reducer / flattener built into the focuser. Therefore like any other 'scope with a reducer / flattener you have to get the spacing right. It's just a pity that TS don't seem to know the correct value and release the thing with optics that aren't square or even possibly centered.

*sniffs* Dagenham, 'cos it's beyond Barking. Sorry, (West) Londoners' joke.

There are bench tests for optical alignment, but they're a bit specialised, Zygo interferometers etc. The optical elements can be parallel to each other, but if they're not centered then the stars will not be round. And if the elements are not correctly spaced there certainly will be errors, quite severe ones.

That would be money well spent in my opinion. Having had my fingers burned over this 'scope I'm more wary of buying in the future. I note the Altair Wave series of 'scopes come with a test report so you do at least know what you're getting. Debating with myself whether to see if I can send it off to Es Reid to find out exactly what's going on.

No Olly, I wouldn't shoot you down in flames, I think TS (Or whoever makes these things) has been a bit optimistic in pushing it to f/4.4 when an even 5.0 would have saved a lot of problems. They have another couple of these 3+3 designs working at 5.1, and 5.0. My Megrez 90 with 0.8 reducer reaches f/5.3and gives a much better image than this. The problems WO had with their original 71mm f/4.9 gives weight to your argument. I think my next 'scope will likely be a 130 f/7 Triplet Apo, with a flattener and a 0.79 or possibly 0.75 (Riccardi) reducer. Meanwhile I need to gather more evidence of the defects in my example before emailing TS to seek a resolution. Blast these cloudy nights.

I did have an email from TS just after I'd bought it as the outer box said 80mm f/6 and I wanted clarification. Apparently it starts life as a bog-standard 80mm f/6 then has a reducer fitted to bring it down to f/4.4. I've put this on the back-burner until I get longer dark as I'm fed up with bashing my head against this thing (Or even the wall) at stupid o/c. I'm back to using the Meg 90 and reducer.

Good review Paul. As the other member here with one of these I can confirm everything Paul has written. This thing is *very* sensitive to spacing, and you'll need that fine focus knob as you can go through focus and out the other side very easily. ATM I'm working on 84mm from the m68 thread and leaving out the rotator, but I have tilt in my Trius that hadn't been a problem before but is giving problems now.

Just a quick snap. In the background my Megrez 90 f/6.9, in the foreground my new 80mm f/4.4 six-element astrograph.

A Rosette from the beginning of 2015 2 hours each of H-alpha and [NII] plus 4 hours of the much weaker [OIII] signal, mapped Hydrogen to red, Nitrogen to green and Oxygen to blue, all in 600 sec subs with the Megrez 90 and 0.8 focal reducer / flattener through 3 nm Astrodons. Guiding with PHD2, capture and post in Astro Art 5

Ooh, is that the Neo-Achromat, quasi Petzval design? I've often considered that for NB imaging though I think it would have too much CA for LRGB work.

Seriously, as has been said don't spend a penny on hardware until you've bought, and read *thoroughly* "Making Every Photon Count* Here; http://www.firstlightoptics.com/books/making-every-photon-count-steve-richards.html AP is so counter-intuitive it's very easy to spend a silly amount of money, only to find you have to go back to the beginning and start again. Then again, even when you do know, it's even easier to spend a silly amount of money .

I have a Pulsar pier (The one in the video) and TBH the lack of adjustment doesn't bother me. I made sure the mounting block it was going on was reasonably level and after that it was a first iteration with the Eqmod PA tool then drift align in PHD2. TBH I need to give it a few more iterations of drifting and then a 3 star alignment, when we have a clear night with little or no Moon. Yearh, right

Nah, you just need more (And longer) subs

Well, I dunno about that, I never could get on with alt-az, right from the off, seemed daft to push a 'scope around in two axis when you need only do one. And now I've turned to the dark side there's no going back.

Here's mine. Megrez 90, 621mm fl on HEQ5 with ST80 guide scope

The Baader MPCC will force the focus tube too far in as well when used with filter wheel and Trius 694.

Thanks Louise. It's looking as though it'll be a while till the next clear night. Hopefully I'll have time to learn.

Well I've downloaded and installed Astrotortilla. Now to work out how to use it

I think I'll have a look at Astrotortilla, though AA5 is supposed to do plate-solving, if only I could find a star-map for it.

Yeah, got a lot of work to do. I've a RDF on my Megrez but it won't fit the 130 unfortunately, something more to buy. I'd hoped to get away without adding counterweights, but I guess I'll just have to bite the bullet and put some lead on the rig. Something like M44 has a nice field of stars and is well placed ATM so might make a good target for testing flatness of field. The PA could do with a tweak I think as the guide graph looked pretty horrible.

Yes, I'm using a Baader MPCC. I think part of the problem was down to my haste and, yes, laziness. I'd been using the Baader L filter for my first trials the previous night, then switched to the Astrodon Ha for this image. The first trial exposure had looked OK so I went ahead with this run. In hindsight I should have slewed to Betelgeuse and touched up the focus with my Bahtinov mask, but I'd been faffing around so much and I wanted to get this run in and the kit put away before turning in myself that I skimped the final touch. I set up not long after I got home from work about 5.30 or so but it was turned 9 o/c before I had M42 in the field and was ready to start imaging. Most of this delay was due to actually finding my target what with meridian reversals and not having any kind of finder on the 'scope. I think a few more adjustments need to be made, along with fitting a finder. If I do fit a finder I'll also need to add some counterweights to the tube to balance the camera and filterwheel.

Real First Light! After much faffing around I managed 12 x 240 sec subs of M42 through 3 nm Ha Unfortunately the focus was a bit off, probably in my haste as my imaging time was slipping away and didn't take time to slew to Betelgeuse and refine focus with the Bahtinov mask. The stars are a bit soft and I see some doubled diffraction spikes. When the moon moves out of the way I'll be having a go at some of the brighter galaxies, ones that I might stand a chance of imaging through this horrid orange murk.

I had first light with my 130 P-DS last night, but nothing to write home about, just getting focus and stuff. Did get an image of the moon, but so near full it's not worth posting. May have another go tonight if it holds clear.

*picks jaw up from the floor* Words fail, totally.

Oh my word!