Picked up an Evostar 90 today.....

[stan26]

Was on my way back from Peterborough to Stowmarket and had a bit of time to kill, no kids with me either! so took a slight detour to Ely to visit the national astronomy centre (scopes n skies/pulsar optics). Had no real intention to buy anything but wanted to look at an Evostar 90 to get an idea of weight etc, I'm thinking of a long FL budget imaging scope, and plus I want a grab n go scope for lunar viewing. I couldn't see one in the showroom and ask a member of staff if they had any in stock, he went out the back to check, meanwhile I spotted a slightly dusty blue refractor tube laying on some sort of base in amongst some huge dobs, I picked it up and it was a 90. The guy returned and I asked the question "is this for sale..?" Looking a bit confused he asked his colleague and it turns out that the mount was sold separately (with the rings?) leaving just the OTA but no EP's or finder. He said they wanted £70 for it. I tried my luck with an offer of £50, and in the end we met at a £60 deal for it. The optics are 100% as new, the tube is unmarked with just a light covering of dust where it had stood in the showroom. Ok it has no mount but I already have that anyway, so if I did buy a new one (which comes with mount only) the mount wouldn't get used, so saving over half the price I would pay I think I'm on for a winner!

Had my first light with it tonight through gaps in the cloud. Mars & Venus where lovely and crisp with a lot less CA than I expected. The only thing that bothers me is the very prominent diffraction spikes on bright stars/plantes....is this normal for refractor of this spec...? Other than this its fine, id say even at full retail the scope seems excellent value for money. I can't way to get some lunar viewing done with it.

They also had a TAL100RS in the showroom:cool:....man I want one!

A few pics during first light....

[JamesF]

Can't imagine why you'd get diffraction spikes with a refractor. Most odd.

James

[ollypenrice]

The diff spikes will be caused by the metal lens clips. William Optics managed to make this mistake on one of their expensive refractors. It should be very easy to eliminate; just make a small front aperture mask to stop down the lens enough to hide the clips from the light path. I make such masks to stop down camera lenses from the front. You just need a cheap compass cutter from a graphics shop and some thin plastic or acetate sheet sprayed matt black. In fact you might get away with just a ring of self adhesive draft excluder foam, sprayed black, and stuck around the inside of the dew sheild.

Olly

PS, Stan, your setup looks so inviting set against the sky in those pictures. Nothing looks finer than a telescope against the night sky!

[stan26]

The diff spikes will be caused by the metal lens clips. William Optics managed to make this mistake on one of their expensive refractors. It should be very easy to eliminate; just make a small front aperture mask to stop down the lens enough to hide the clips from the light path. I make such masks to stop down camera lenses from the front. You just need a cheap compass cutter from a graphics shop and some thin plastic or acetate sheet sprayed matt black. In fact you might get away with just a ring of self adhesive draft excluder foam, sprayed black, and stuck around the inside of the dew sheild.

Olly

PS, Stan, your setup looks so inviting set against the sky in those pictures. Nothing looks finer than a telescope against the night sky!

Hi Olly, thanks for your reply. My first thought was exactly what you say, and yes it has got the 3 clips that protrude into the lens aperture, However I did a little test by fitting the lens cap and pushing out the centre cap making the front aperture about 2.5" I guess, given me effectively an F15 scope. This did not make any difference at all. Plus should I expect to see 3 spikes like the Mercedes benz star if it was caused by the 3 clips..? I think it may be caused by my "erecting prism" diagonal that came with my Star travel 102. This is the only 1.25" diag I have hense using it. I googled the problem and found a thread on CN forum where a member had the same issue. It was suggested that the roof angle of the prism creates the diffraction effect.........

I did have a look through my ST102 before I packed away using the same diag/EP's/barlow etc and was suprised to see a horizontal diffraction line right through Mars.........hmm...

P.S, I agree about the scope and night sky pics, they just look great don't they, especially a classic long refractor! I just wish it was a TAL on there........

Stan

[nightfisher]

It does look good against the night sky, your becoming a Tal fan:D

so how about this beauty? its the new 150 APO goto

[ollypenrice]

I've always found that the erecting prisms give an excellent result in the daytime but are disastrous on the night sky. I always wanted to learn my way around the moon with an erecting prism in the scope but the image quality really nose dived. It's a shame. I bet you are right, it will be the prism if it isn't the clips.

Olly

[stan26]

It does look good against the night sky, your becoming a Tal fan:D

so how about this beauty? its the new 150 APO goto

I have wanted a 100RS since there release. They just look so right, I love classic refractors. Yesterday was the first time I actually got to look at one. I think it was the build quality that got me, the focuser is superb and has a real quality precision engineered feel about it. I haven't looked through one yet....one day hopefully I will get to look through my own........

[stan26]

I've always found that the erecting prisms give an excellent result in the daytime but are disastrous on the night sky. I always wanted to learn my way around the moon with an erecting prism in the scope but the image quality really nose dived. It's a shame. I bet you are right, it will be the prism if it isn't the clips.

Olly

That's interesting, I think a new diagonal will be next on the list.....

Thanks

Stan

[John]

My refractors (Vixed ED120 and Skywatcher ED120) both use the foil tabs in the objective lens but I've never noticed any diffraction spikes from them in visual observing

I've heard they can cause issues when imaging though.

My guess would be that the culprit is the erecting prism diagonal.

It will be very interesting to see if that TAL 150 makes it onto the market. The TAL Apolar 125 had great potential I reckon but the two I tried had QC issues (one, serious ones) which really surprised me for what was, at the time, a flagship model.

[Alkaid]

Yeah, the Evo 90 is a very nice scope, I love it's light weight and zero faff.

[Marki]

It will be very interesting to see if that TAL 150 makes it onto the market. The TAL Apolar 125 had great potential I reckon but the two I tried had QC issues (one, serious ones) which really surprised me for what was, at the time, a flagship model.

Definitely would want to take a look at this if it comes over here. Hopefully the issues John reported in his reviw of the 125 wouldn't be present now... .

[stan26]

Ok, its not the star diag causing the diffraction. I looked at a bright star and mars without the diag, just placed the EP into the end of the scope and still the diffraction was there. I checked and cleaned the lens, check the inner tube for loose baffles etc, but nothing! I took this pic with my DSLR that clearly shows the diff spike pattern. Could this be caused by faulty optics? Looking down the tube from the front I'm not convinced everything is lined up, i.e the focuser seems a little off to one side.....?