24 replies to this topic

[ippiu]

Hi to all.

I'm really tempted by this scope just for imaging (i don't do visual).

I don't find anywhere, either on the web, or on Askar site, which glass the lens are made of: from the price, it seems it's Fpl53.

Does anybody confirm this?

http://www.askarlens...roduct/208.html

 

Thanks 

Edited by ippiu, 15 November 2020 - 12:33 PM.

[MikiSJ]

I believe Petzval lenses have 4 or 5 elements, not three.

 

See a description at https://en.wikipedia...ki/Petzval_lens

[ippiu]

I believe Petzval lenses have 4 or 5 elements, not three.

 

See a description at https://en.wikipedia...ki/Petzval_lens

yes, sure...

But i mean the glass of the triplet obviously...The other 2 lenses are for correct the field and make it a flat field...

[junomike]

Made by Sharpstar.

IME If it's made with FPL-53/55 or something similar, It's listed as such.

[amery]

I'm also highly tempted by this sharpstar, with the reducer becomes f3.9!, but I don't know if my CEM40 can handle it 😥

[amery]

Made by Sharpstar.

IME If it's made with FPL-53/55 or something similar, It's listed as such.

anyone knows what's the FRA400 made of? they don't list it either

[amery]

teleskop-express.de listed it in this forum as FPL53. https://forum.astron...b-lager.297593/

 

German and Italian distributors now list it as in stock, for 2700€

 

opinions?

Edited by amery, 16 November 2020 - 11:41 PM.

[ippiu]

I'm also highly tempted by this sharpstar, with the reducer becomes f3.9!, but I don't know if my CEM40 can handle it

I have cem40 and in the beginning i would have liked to buy APM140 doublet....But this scope is over the limit for the cem40, for sure not the askar fra600 that for me it's the perfect combo for cem40.

I have the triplet 115/800 on cem40: no problem and a good combo...

[ippiu]

teleskop-express.de listed it in this forum as FPL53. https://forum.astron...b-lager.297593/

 

German and Italian distributors now list it as in stock, for 2700€

 

opinions?

I'm Italian but no italian seller has it in stock...

For what i know from 2 italian sellers, just TS has it in stock....

[amery]

I'm Italian but no italian seller has it in stock...

For what i know from 2 italian sellers, just TS has it in stock....

I thought I saw it available at telescopi-artesky.it last night :-/

[amery]

I have cem40 and in the beginning i would have liked to buy APM140 doublet....But this scope is over the limit for the cem40, for sure not the askar fra600 that for me it's the perfect combo for cem40.

I have the triplet 115/800 on cem40: no problem and a good combo...

may I ask what 115/800 do you refer to? ;-)

[ippiu]

I thought I saw it available at telescopi-artesky.it last night :-/

no...not yet...https://www.telescop...5517136157.html

Just TS has it in stock...

 

may I ask what 115/800 do you refer to? ;-)

https://www.tecnosky...115-800-v2.html

[ippiu]

I wrote to TS germany and asked about fpl53 fra600 lenses.... This is their answer...

thank you for your request.

No, the ASKAR 108mm does not use FPL-53 glass, however its color correction is very comparable to FPL-53. It's a Petzval "special glass".

Have a good day!

Kind regards


Simon Großlercher

[sl-he]

No, the ASKAR 108mm does not use FPL-53 glass, however its color correction is very comparable to FPL-53. It's a Petzval "special glass".

With this answer they confused us even more 

[amery]

With this answer they confused us even more 

the one I got from TS was a better:

 

 

 

Hello,

it's not declared because they use chinese glasses. From the informations I have, the chinese glass are almost equivalent to the ones from Ohara in terms of quality and Abbe number. I expect they could be like lanthan glasses, so very close to FPL-53. As well they use 2 of these glasses and the correction provided is very good. if you have any question I'm here,

[j1will]

the one I got from TS was a better:

I own the Askar FRA400 and am getting excellent results from it, including in depth pixel level post editing.  It's my understanding that now Hoya and perhaps some other glass for lens manufacturers are achieving the same level of performance but can't refer to it by the exact same nomenclature as with the Ohara glass?  I'm looking at either the Askar FRA600 or the Sharpstar 121mm f/5.6 Quintuplet to add to my range.  Probably the 121mm would be a better step in focal length before jumping to the SCT scope ranges for me.

[ippiu]

I ordered one....

I can't wait to have it....but until 5th december, i can't pick it up....

[Uggbits]

I received mine today. I managed to do a quick visual look between clouds at the moon and a couple planets. It looks promising so far, but it is now just a waiting game for some clear skies and proper testing.

 

Cheers, 

Dan 

[amery]

I received mine today.

that was quick, keep us posted!

Edited by amery, 24 November 2020 - 05:02 AM.

[Uggbits]

So, I have had it out for two nights now. My general take is that it isn't perfect, but I'm not terribly disappointed either. That seems to be about balance for a scope positioned the way this one is in the market. The only lingering worry is how it will behave with the reducer once that is available, as that is one of the perks to this tube over some competing options.

 

The good: the field at f5.6 is quite flat, to the point of very minor FWHM shifts across the frame that look to be focuser sag. It is well illuminated, and the mechanical elements of the system seem to do their jobs (with a minor note below). 

 

The so so: there is some minor chromatic aberration if you pixel peep. I think it may be slightly clearer due to my use of an Hutech NB1 filter during my shots, but it is there. It is easiest to pick out by looking at the isolated channels in Pixinsight, where both blue and green match well, but red is slightly narrower and elongated in the corners. This aligns fairly well with the spot diagram.

 

There is also a very slight amount of sag and image shift in the focuser. It is overall quite good, holding my camera steady without me locking it down, even at the zenith. I will try locking it for the next session to see if it improves the sag.

 

The slight tilt in the system produced some issues for the stars on the bottom left, which did not appear to be as bad on the second night. I've also observed similar distortion from the NB1 filter on my 100-400 lens at f5.6 and using my 105mm at 1.4, so I'm not quite as concerned about that just yet.

 

The mosaic below is a slightly cropped field from my Ra, so it is just between a full-frame and APSC field. I had to crop because the meridian flip killed the alignment in the stack. I will share a single frame example later. 

 

 

 

Cheers, 

Dan

[RogeZ]

Dan:

That is very good Mine should be here in 2 weeks

[ippiu]

There is also a very slight amount of sag and image shift in the focuser. It is overall quite good, holding my camera steady without me locking it down, even at the zenith. I will try locking it for the next session to see if it improves the sag.

 

For a such expensive apo triplet scope, for me this is unacceptable...

Considering that on lower cost 2,5" RP focuser this image shift was never found...Probably i ask for a refund from TS...

 

https://drive.google...iew?usp=sharing

Edited by ippiu, 05 December 2020 - 05:14 AM.

[ippiu]

Inside the n° 6 screw hole....(with M4 small screw removed) 

http://www.askarlens...class7/208.html

you can see a sign left by tightening the M4 screw against focuser metal plate

 

While focusing by coarse and fine knob (this time by hand) you can see this sign that moves back and forth while changing focuser direction...

https://drive.google...iew?usp=sharing

Edited by ippiu, 05 December 2020 - 08:38 AM.

[Uggbits]

I didn't play around too much with the focuser because my main concern was to evaluate the optics. I did note that different pointing angles contributed to whether or not there was any focus shift while racking in and out. The level of shift is about the same as a Televue NP127is focuser on our old club scope, but looks to be a bit more than my 2" Feathertouch Crayford (which aren't particularly amazing). 

 

I'm generally pleased with the optics. I took a shot without the NB1 filter, so I will share an aberration mozaic from an unprocessed frame later today. 

 

Cheers,

Dan

[Uggbits]

As mentioned in my prior post, the focuser does appear to have a minor amount of sag. In any case, this is a single 3 minute subframe with my Canon Ra (about 2"/pixel) without any filters. This is early in the evening, so my focus shifted slightly and despite focusing in the centre of the field it looks like the corners were starting to improve at the cost of the centre. 

 

In addition, there are some spikes on stars in the corners. I suspect this is astigmatism introduced by a vignette from my EF-RF adapter. It's something I will need to compare to using my old 6D or a straight RF t-ring if I can find one.  

 

 

 

Cheers, 

Dan