Altair Astro Wave Series 115 ED triplet APO

[fwm891]

Well rain is forecast again as within 1 hour of this scope landing on my door step it started raining - no change there then

OK this is the OTA only no flattener/reducer or other optics in the light path.

Weather (as fore mentioned grey-overcast)

I put the OTA on a static tripod and fitted my full frame Nikon to it and framed up on my favourite tree (used to focus the MN190, oag and align finder etc).

Camera set to manual mode, ISO 800 and shutter constant at 1/2000th sec for every shot. Files: Fine jpg. 4256x2832 pixels

Tree was positioned centrally then in each corner

Files then opened in PS CS3 and a 700x700 pixel square was copied from each frame with the tree in a corner and pasted onto the full frame image with tree central - no other processing has been done to these files

A full frame was reduced in size to show the small amount of vignette in each corner - remember NO FLATTENER has been used (I'm still waiting for that to arrive).

My first impressions looking at the full size jpg files and at the weather outside is one of elation. I didn't expect to be able to see the power lines go from edge to edge of the frame with only minimal degradation.

Altair's website details mention slight vignettes to the corners of full frame chips so that was expected - although its less than feared.

Tree repositioned by using the tripod pan/tilt and scope focus was locked when the central image was framed

Looking forward to getting the flattener and repeating the test (weathers bound to oblige )

APS chips may not need a flattener... Need to try my Atik 383L+ mono out on this

I have attached an annotated image of the test panel.

Francis

[michael.h.f.wilkinson]

Very nice. Hope the skies clear soon

[fwm891]

Added Nikon DX and Canon APS-C frame sizes for comparison - sizes taken from Wikipedia CCD frame comparison schematic

[iksose7]

Unlucky about the weather, but at least you have an awesome scope to look forward to using! I plan on buying the 115 next year, or maybe the 102. They sound like fantastic scopes which is why i want one of them to be my first. Would be nice to see a review once you've settled in, theres not much out there other than Olly review which is great but the more the merrier!

[fwm891]

I've added my Atik 383L+ to this image as a further comparison:

Not sure I'll need the field flattener with the Atik, but will for the full frame shots.

[spudlet]

This might sound a really trivial question to ask but how are you finding the screw on lens cap? I am finding mine to be a real devil to use. Screwing the damn thing back on without crossing the threads is an art in itself it seems.

[kingboya]

This might sound a really trivial question to ask but how are you finding the screw on lens cap? I am finding mine to be a real devil to use. Screwing the damn thing back on without crossing the threads is an art in itself it seems.

The lens cap is very fiddly to put on. The thread is just too fine. If it was bigger, it wouldn't have been such a problem I reckon. Ah well, small price to pay.

[ollypenrice]

Looks like you have a fighting chance of getting away without the flattener, Francis, and that would be convenient if nothing else. I never tried this scope without the flattener, for some reason. Bit silly of me in retrospect!

Olly

[fwm891]

Re: the lens cap - noisy and takes ages if you use the full thread length. A bayonet style would have been much better.

Olly: I've now had chance to do some star testing without the flattener - see what you think...

Could have saved myself £140 had I known it was going to be that flat across the 383L. Though if I put the full frame Nikon on the back I definitely need the flattener.

Larger file on my flickr page

[spudlet]

That's a nice image!

I am hoping I can use mine without a flattener (in any case I didn't purchase one originally with my scope as my astro-photography is only very casual, wasn't wroth the extra cost). Your tests shots are impressive and have finally spurred me on to hook up my EOS350D to my scope.

[fwm891]

You may just loose the corners slightly but with my 8300 chip (which is slightly smaller the stars are good right across the frame.

Use a Bahtinov mask to focus with, and position a star about ½ way across the frame as its quite critical. Then re-frame your image. - good luck

[Dougie]

I bought the 102 after reading Olly's review in one of the popular Astro mags.

Overall pleased with the scope, but the lens cap does take a long time to screw in and yes it is noisy, particularly at 2.00 am in the morning.

When it's late, I tend to put a temporary cap on until the morning.

I have the flattener but I'm still getting elongated stars in the corners.

Had the camera checked by Terry at SX using his laser, so that wasn't the problem.

I'm going to try and adjust the tilt of the camera this weekend with the help of CCDInspector.

Hopefully it will improve things.

[fwm891]

Hi Doug, Is it a spacing issue. Blurb says there's quite a wide tolerance with the flatteners ± 5 mm (I think) maybe more for small CCD's.

Still waiting for a Nikon adapter so i can try out the flattener, so far I've been shooting without and not complaining when capturing on the Atik 383L.

[ollypenrice]

Looks good to me Francis. Forget the flattener and enjoy freedom from chip distance faffings! Doug, could the flattener be introducing problems because of the chip distance? This does have to be right. In theory a wrong chip distance using a FF/FR would give a uniform distortion into all four corners but in reality that tends not to happen. You'll get a distortion across the top or into one corner, etc.

Olly

[Davey-T]

Re: the lens cap - noisy and takes ages if you use the full thread length. A bayonet style would have been much better.

Well could be worse, I've just purchased a William Optic FLT110 with a push on cap and if you fit it before sliding the dew shield back it blows it off the end landing with a nice crash on the concrete and chipping the pretty gold paint

Dave

[Dougie]

OllOOlly, I was using the recommended distance of 51.5mm suggested by Altair less the 17mm from camera face to chip given by SX. With two spacers and the IDAS filter, I have 34.5mm. I've checked all screw fittings for flex and everything appears tight. I did try using the adjustment screws on the camera, but only made matters worse, hence Terry at SX putting things right for me. Now bought a separate tilt adjuster so I can't mess up the camera and giving it a try tomorrow night.

[ollypenrice]

OllOOlly, I was using the recommended distance of 51.5mm suggested by Altair less the 17mm from camera face to chip given by SX. With two spacers and the IDAS filter, I have 34.5mm. I've checked all screw fittings for flex and everything appears tight. I did try using the adjustment screws on the camera, but only made matters worse, hence Terry at SX putting things right for me. Now bought a separate tilt adjuster so I can't mess up the camera and giving it a try tomorrow night.

The tilt adjuster is a good idea in principle but the other thing is that each filter in the system has an effect on the distance. This may also be having an effect. But I don't follow your sums on the chip distance. What do you reckon your present chip distance is, all parts included?

Olly

[Dougie]

The distance I have from the rear flat shoulder of the flattener to the chip is 51.5mm with all parts included

I never thought about the filter in the image train having an impact.

[ollypenrice]

The distance I have from the rear flat shoulder of the flattener to the chip is 51.5mm with all parts included

I never thought about the filter in the image train having an impact.

You might add about a mm per filter, I think, but it shouldn't be terribly critical.

The other possibility, maybe, is that the front cell is not aiming the beam onto the centre of the chip. It is easy, in principle, to tune that out using the push-pull screws on this design.

Olly

[Dougie]

I managed to get the tilt sorted but I do have slightly elongated stars in one corner.

CCDInspector is showing no tilt bit a slight curvature at one end.

But I suspose that's the problem using an M26C camera.

I will later this year be adding a smaller chip camera to my equipement, so elongated stars should not be a problem

[fwm891]

Doug,

The only thing I can think is that your OA is not central with the physical tube, adapters etc and that when you tilt the camera plane you line the camera with the scope focal plane but because the OA is not central your now outside the corrected field size in one corner?

The optics may be physically collimated with themselves but not with the body of the scope. I doubt it would need much of a displacement to cause the problems

[Dougie]

Francis

You may be right, but not sure how to correct it, if it is correctable.

Or is it a fault in the flattener?

[fwm891]

Doug - do you get the same-off centre effects without the flattener?

[spudlet]

I did some test shots last night with my eos 350d, just a stack of half a dozen 20s exposures. Pleased with the result:

[Dougie]

Spudlet, test results look good.

Are these taken with the reducer in place?

Francis, I haven't tried without the flattener, but I should give it a try.

The only problem will be trying to get the focus right.

I took 2hrs 20 minutes of data last night on M31 which I now need to process, except work is taking priority for the next week.

If the image is half decent, I'll post so that you can see the issue I get in the corner.