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My Istar 127mm f/8 Refractor build .


Brian Nordstrom
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Nice photos Brian and an interesting story about the NP127 owners invitation - it will be fascinating to see how the comparison goes  :smiley:

Your scope does seem to show exceptionally low levels of CA for a 5" F/8 achromat. I wonder how this is done as my understanding is that the levels of CA generated by crown and flint doublet achromats is, by and large, a matter of physics ?.

Do you think you have got one of the R30 or R35 objectives by mistake ?

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John , I don't know about getting a R30 by mistake , but yes my lense is a really good one when it comes to CA control . SA is nearly non-existant as well ,just a tiny bit of over correction , nice .

Yes there is a faint purple ring around venus but it is very thin and so dark it is easy to overlook , in my eyes anyway , the photo shows it well .

What gets me is that there is no 'Blue' one side and 'Red the other ?? yes its a great piece of glass , Istar sel great stuff , as you would know seeing as you have a 6 inch f12 .

By the way how does yours perform ? , I have a mate down here who is building one , his 6inch f12 objective arrived from Istar the other day , he is very excited .

Thanks .

Brian.

Edited by Brian Nordstrom
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My 6" F/12 Istar seems to perform very well Brian, from the brief star testing I've done with it on a less ideal mount. It does show some CA of course as all achromats will  - I'd have to have something around F/18 to make it invisible to the eye and F/12 is quite large enough, believe me :rolleyes2:. The CA is pretty much as I expected from the table below and less than the F/9.4 127mm achros that I've owned in the past. It should be a bit less than your 127mm F/8 achro too but, from your description, yours seems to be pretty CA-free which is amazing for an F/8 achromat, which is why I queried it.

SA seems very well controlled in my scope too.

I do need to get the scope on a more suitable mount though and I'm working on that. 

Here is that table, which I find reasonably accurate from the achromats I've owned:

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Standard  CA ? food for thought .

By the way last Saturday night John was  pretty average , Clayton did not bring his NP127 , as I did not bring my Istar 127 , I took my M210 instead , glad I did 150x was the max  the Tak could use , it was a [removed word] , maybe this Saturday night , new moon ..

I hope .

Brian

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Great bit of reading John , heavy duty but it makes sense when you read the whole article .

We  had the first rain of the wet season last night , but its a glorious day here today , the bit of rain washed all the burn off smoke out of the sky , hope its good for tomorrow night ??? .

I will do a report if it happens as this will probably be the last for 5 months , wet season !!! .

Brian.

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  • 6 months later...

Well , while I am here I might as well post a short report from Saturday night 2 weeks ago . A good friend of mine from Victoria , South Australia is retired and crusing Aussie as a 'Grey Nomad' he hit Darwin 3 weeks ago .

a couple of Saturdays ago , 1st june I spent the day super charging his 150mm f8 Sky Watcher frak . And did it need it or what !!! he has not used it since he got it second hand , it was almost un-useable , SHAME!! on the seller ! . It was a shocker and Peter has only been into astronomy a few years and did not realise the state of his buy . Shame .

Anyway a full day , many coffie's and a few beers later Peter's scope was usable , I gave him the SW s/s tripod that came with my HEQ5 .

It fits his lovely Vixen GP well and gives him 150mm of much needed hight .

Note the extra white counter weight , I made that a few years ago and the 150mm OTA is way to heavy for the 2 Vixen C/W's , also note the OTA is sitting about mid-ships on the mount ? I e-poxied about 2 lbs of lead fishing sinkers into the focuser housing to allow this , Peter was impressed as you can see in one of the photos where he is sitting and admiring his sexy telescope that now works . He is a happy camper now and that makes me feel good .

Later that night we had a shootout , Peter's 150mm f8 SW'r and my 127mm f8 Saxon/Istar .

As good as the 150mm is its performance is in another league , compared to the 127mm Istar , the Istar gave better views of Saturn at 300x , double stars , clusters to the edge , and above all the stars looked much nicer in the Istars 127mm .

the only thing Peters 150mm SW'r won on was deep sky , the extra 25mm is a lot and his scope was better here by a wide margin .

I wont bag the 150mm , because if the test was not done side by side the Istars nicer imagers would not be seen , that's how good these Synta 6 inch f8 fraks are , very good but the Istars lense is a lot better .

I used my 3mm TV radian to get to 333x and Peter used his Meade series 400 plossl 4mm at 300x , we only used this magnification on Saturn and alpha centarui ( double star system ) most testing was done with me using my 9mm Nagler and 22mm Panoptic , and Peter used his 18mm Meade series 5000 and 9.7mm Meade series 4000 ( awesome eyepiece that one ! )

We finished about 4 am tired , but happy , a great night and here is a few photos .

The last one was after 4amm , awesome .

Brian.

Man I love these photos , I will post more of this perfect day .

Brian

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In that first photo I had to look at it a few times before I got the perspective right :rolleyes: .

Lovely looking scope :)

Thanks Naemeth , how's about a thread (pole) on the worlds sexiest telescope ?

Here is mine and the .79  day old moon setting in twilight , she has great contrast  .

Taken as I waited for the big boys to set up .

And the first photo is taken here in Perth on a dark sky night ,,, twilight  again ,,, it is an awesome spot .

Brian.

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Edited by Brian Nordstrom
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Thanks Marki and Naemeth , I posted those 2 scope photos to show the difference between the altitude settings or Darwin 12 degrees south  (2nd photo) and Perth (32 degrees  south) shows how big this beautiful continent of Australia is .

I love my Istar and if I could only have one scope ,,, this would be it .

Thanks again guys .

Brian.

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Partial Solar eclipse today here in Perth ,starts at 1.17pm and finishes at 4.30pm 59% coverage , I have my Istar ready to set up with Lunt Hershell wedge .

Hope the clouds clear , but its looking promising , lots of clear skies between the high clouds .

I will post photos later on today , wish us luck .

Brian.

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As promised here is a few shots or todays  partial solar eclipse from here in Perth Australia .

First  contact was 1.17pm and last was 4pm with 59% at maximum .

These photos are mainly the scope and Hershell wedge set up as I will post most good photos of the eclipse itself  in the solar section ,, tomorrow as I left the scope out and I AM ENJOYING PROBSBLY THE BEST VIEWS OF Mars and Saturn I have ever seen , both at 300x with my 3mm TV Radian tonight is so dark and still  , easily a 9 out of 10 .

 Here are a few photos of the  'mighty'  127mm f8 Istar doublet in action  , man this in a great telescope !!!.

Brian.

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  • 4 months later...

Update , I ordered a hand made solid wooden scope case for my iStar 127mm f8 and it happened to arrive a few days after the iStar decals that Mike of iStar optical USA sent out free of charge to any iStar scope builders world wide , a great gesture .

Here is the case and decals fitted on the OTA , hope you all enjoy .

The case was only $299au and was custom made to fit the iStar's dimension's and that it does perfectly , it will protect the OTA for many , many years .

I will now call the iStar officially finished ??? .

Comments welcome , as always .

Brian.

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  • 4 months later...

Up-date ! , I have since my last post grabbed a nice 2nd hand SV 90 degree finder ,  great optics and build and being able to   take standard 1 1/4 inch eyepieces I have taken it to nearly 100x and its still sharp , impressive to say the least !.

It took some getting used to  , but my neck thanks me now , very easy to use .

I also had a plaque made up for the case , a nice finishing touch I think .

Enjoy.

Brian.

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  • 2 weeks later...
  • 1 year later...

My God !!! how time flies ,,, 

Another update to the beautiful iStar 127mm f8 achromat  build .

Ok , first up is I scored a lovely Sky Watcher Esprit 120mm f7 APO focuser off a fellow IIS'r for a steal after he upgraded to FT , , it did not fit straight up but a small spacer was made to have it fit the Saxon's tube  and at 3 inches in diameter at the rack ,,, its a large R&P Liner style that's very nice in use and suites the scope well .

Number two is the awsome Celestron CI700 mount , this thing is a ROCK !!! of stability as they were made to hold C14's  and note the position of the counter weight ? and that  speaks volumes .

It's legs are 3 inch diameter that will break a toe if kicked in the dark !! and on that the other night I was looking at the moon at about 250x and smashed my head into the mount drawing blood and the  crater was still centered in the eyepiece , its a monster .

Its only draw back is that it weighs about 70kg ,,,,,,

 

Observatory next ?????

 

Enjoy my friends ..

Brian.

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One more photo as this  one kinda shows the actual physical size of this often overlooked mount  ( rare yes I know ) and yes it is easily on par with Losmandy's lovely ( read Expensive ! ) G11  , enjoy .

Brian.

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Edited by Brian Nordstrom
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