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Altair/GSO RC8 10" Truss MKII - Happy Christmas to me :-)


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I have been surprisingly impressed with my Carbon Tubed 8" F8 RC to convince me to start looking at the 10" Truss Model for deep sky.

I originally wanted one of Peter Shah's 656imaging (http://656imaging.co.uk/) DK Scopes as they are a thing of beauty, but having recently bought the iOptron Mount, Moravian Camera, FW and OAG and the Chroma 3nm filters, the cupboard was almost bare.

Well you can always find money when something comes up and in this instance the credit card took a partial bashing, Ian at Altair Astro sourced me one of the GSO OTA's re-badged as theirs.

I have always found it a pleasure to deal with Ian, he's a small outfit that genuinely cares and I decided rather than risk the OTA getting bashed around with the Christmas couriers that I would take the 199 mile drive over to Ian's place, even though I knew that it is one of the worst drives for me, it's cross country and after Kettering is single garage way, 4 hours later I arrived at this delightful village in Aylsham, Near Norwich.

When I arrived I was amazed how Ian managed to get so much stock into this little historic shop, it was crammed to the ceiling with products, Ian as always stopped everything he was doing and we finally got around to sorting the payment and the dilemma as to how we were going to get this massive box (85cmx50cmx50cm), into my 911, which I had purposely driven, as it's more economical than my other cars and through the winding lanes is a bit of fun.

As a 2+2 is does have rear seats, which are OK if you are a child or as can be seen when I had my 2 boxers (Sadly Storm the bigun passed away last month and I'm still raw?) so I figured that I could put the OTA behind me and break the box down and use that for cushioning, Ian suggested that I take the OTA and all the bits that came with it and he would send the empty box to my home, I gratefully accepted Ian's suggestion, and I then pulled up outside his shop in a narrow high street, dropped the roof down and Ian very kindly lifted the new RC into the back of my car, as I am about to have major surgery on my spine and didn't want to cause more damage.

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Well now to the RC, technical specs are below, this is the MKII version and it is beautifully made, with rich carbon fibre construction and the attention to detail is truly awesome.

Aperture (mm) 254
Aperture ratio (f/) 8
tube diameter (mm) 420
Tube weight (kg) 15,2
Tube construction Truss Tube
Tube length (mm) 735
Tube material Carbon
Type Reflector
Coating multiple
Resolving capacity 0,45
Type of build Ritchey-Chretien
Focal length (mm) 2000
Limit value (mag) 13,8
Light gathering capacity 1320
Max. useful magnification 508

Reflector

reflectivity 99
Secondary mirror diameter (mm) 112
Ventilation for central mirror yes
Secondary mirror material Quartz
Main mirror´s construction hyperbolic
Primary mirror - Material Quartz

Focuser

Connection ( to eyepiece) 3
Type of build Monorail
Gear reduction 1:10 Fine movement

https://www.astroshop.eu/telescopes/gso-ritchey-chretien-rc-254-2000-carbon-ota/p,47237#tab_bar_1_select

I had decided to go for the 10" 2000mm FL as I had an unused Astro Physics 0.67 Focal Reducer, that I could use to drop it down to 1340mm F5.3, and with my Moravian G2-8300 would give me 0.87arcsec/px rather than the 0.59arcsec/px.

The focuser was the only weak spot with any of the GSO RC range of scopes, being a Crayford as well meant that I wanted to change it and rather than compromise, I went for the 3" Feathertouch R&P and added a Pegasus Motor Focuser as I am really impressed with the lads at Pegasus and Ian is the main UK stockist so I knew he would have one in stock.

Ian also supplied a 14" Losmandy plate as I knew that the iOptron CEM60EC was quite critical with balancing and therefore if need be I would change the existing 10" one to the longer version and then I could slide a Losmandy clamp with extra weights on the front for balancing.

Being a truss design, it came with a Shroud. There was also 3 fans behind the primary to extract air and reduce dew on the primary, supplied as well was a Kendrick style dew heater for the secondary, which fastened with a few dobs of silicone on to the rear mirror. now usually owners run the cables over the top of the vanes, but I had a better idea, that I intended to use and afterwards I saw that someone else had adopted this idea on here.

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I had purchased some very thin copper strip, which stuck really firmly on the side of the vanes, I soldered the leads from the dew heater at one end and secured the main feed to the other, then painted with blackboard paint and voila you can hardly see it.

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I then made up a Cat 5 cable to provide control and the power to the focuser, this focuser is brilliant and for under £100 is far cheaper than anything on the market and has a really tidy appearance rather than the ugly lakeside motors that I have on one of my other OTA's, no more untidy multiple cable to the motor and it kept everything so much simpler.

I mounted the Pegasus UPB on the top as I figured rather than my usual trick of fitting extensions under the Losmandy and having everything concealed under there that it might cause greater top heaviness, which moved everything higher by 40mm.

I tidied up all the cables, I need to tidy the power feed to the fans, but that isn't urgent and will be done waiting for the new Galaxy Season, I doubt if I will get to use it yet as there are too many nebula targets queuing up to image due to the terrible clear skies we have been having for the last 10 weeks...it might go on even further with the purchase of all this new kit...sorry ?

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All the best everyone and Have a Merry Christmas.

Edited by Jkulin
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Well done John, it looks like a great scope.

I have been looking at the truss  F8 models also for some time now, to go on my CEM 120.

It will be sometime in the new year

Will be looking forward to seeing how you get on and your opinion of it.

I will forgive you for the clouds.   Have a great Christmas John and new year.

Bob.

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38 minutes ago, Jkulin said:

Thanks Bob, and a Very Happy Christmas to you as well.

How are you getting on with the 120, hopefully good?

Hi John,

The mount up to press has been a delight, every thing is up and running great with the software.

As you know I only have my Star 71 on it at the moment which I know is not that demanding.  I am not doing any auto guideing though as yet, I am seeing how far I can go without, [I might wait till I get a bigger scope on for that].  The go to's and tracking with this mount are very good and also no problem with the flips [as yet]..fingers crossed. I know it is early days yet as we are not getting the weather for all the tests, but I think I am not going to be disappointed with this mount.

Best regards

                 Bob.

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John

It looks like you have a very nice setup there.

I have the RC10C (solid Tube). I needed an additional balance weight as well as moving the Sharpsky focuser controller to the front of the scope. There is a lot of overhang at the back of the scope.

Does your scope have the tilt collimation plate fitted to the rear plate.

Graham

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Hi Graham, funny you should ask that, my mate came round to look at it this afternoon and he said was I aware that it had the built in tilt plate, which I thought was the collimation adjustments for the primary, then I remembered that the primary is fixed so accepted that it must be the built in tilt plate.

When I get a chance I take some more images and post them up.

It certainly is back heavy especially when I connect my camera and FW, but that should be easily resolved when I fit the 14" Losmandy rail and attached the clamp with the weights fitted to it, rather like my 8" Carbon RC: -

image.png.3a3a29a53972df49f55a2b5e711ae747.png

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John

Telescope services list two versions of the 10" truss scope. One with and one without the tilt plate. I thought all the new Truss version had moved over to the Tilt plat version. So yours should have three sets of push-pull screws outside the diameter of the fans for Collimation and three sets of push-pull screws around where the imaging train enters the back of the scope for tilt adjustment.

I fitted the Moonlite tilt plate to my scope (solid tube) and it works great but when I tried the Astro Physics 0.67 Focal Reducer I cannot quite reach focus with the adapter rings removed. As the reducer fits inside the focuser I am going to try adding a spacer to move the reducer further forward. I will have to remove a spacer from between the filter wheel and the focucer to keep the spacing correct.

It was a very deep frost here last night. No sign of condensation on both mirrors, the Kendrick dew heater secondary woks well. This morning (I know its Christmas) I popped into the observatory to check and there was a bit of condensation on the primary. Running the fans for 10 minute clears it. I have never had the need to  run the fans during imaging.

A Great scope your will enjoy it a lot.

Happy Christmas?

Graham

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Hi Graham, Just took a photo and I think my one does have the built in tilt plate: -

image.png.975caed4e4367f751f6893b17c10f08c.png

Mine came with 2 x 1" Spacers and 1 x 2" Spacer, I reckon I should be able to achieve focus by removing the 1" Spacer and extending the focuser out by an additional 1/2" but won't know for sure when I will get some clear nights to play.

Wishing you a Very Merry Clear Christmas.

Edited by Jkulin
typo
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" into my 911, which I had purposely driven, as it's more economical than my other cars "

That comment made me smile.

 

I look forward to seeing some images. 

Synta/Skywatcher have revolutionised amateur astronomy market in their sectors in the  last 10 years.  Are we seeing the same thing with the RC market?

 

 

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Owning two RC's certainly was more viable for my wallet that many of the high quality branded RC's out there, it will probably be a while before I use it as currently my targets needed a wider FOV, so I doubt it will be used until February.

GSO have certainly been pushing their range for a number of years, I looked and searched on Astrobin as the quality and number of images taken with GSO RC's and it really was a considerable number, which influenced my buying decision.

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Lovely scope, I have looked into getting one of those for small objects. However, the skies of late have hardly been conducive to splurging more hard-earned on this.

On another note, two dogs on the back seat of a 911? ?  Dude, do you know how much they cost to reupholster?   I am very sorry to hear of Storm's passing :( 

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Hi Steve, If ever you are over my way, stop in for a coffee and you are welcome to have a play with it to see if it suits your needs.

Yeah I know about the interior, it's fairly tough and once they had a seatbelt around them they didn't move around much ? Thanks for your kind words about Storm, one minute he was here with nothing visibly wrong and the next day a brain tumour and we had to say goodbye?, he was a legend, not once did he ever lift his leg against my pier, used to talk to us and tell us when he wanted something and especially told us when he didn't want to get off the settee or drop a rotten apple in the garden, raw is an understatement, so trying to keep my mind busy, AP has helped keep my mind occupied.

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John,

The plain of my CCD is 247mm from the back plate. This maybe a little different on your scope as yours has a flat rear plate. TS quote 250mm for your scope. TS also state that removing 1 25mm spacer should bring the scope to focuse when using the focal reducer. I did not find this. So a little more experiment is required.

Hope this helps

Graham

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Thanks Graham, I don't plan on messing around with the FR until I have got it working perfectly without and with a nice V Curve and the Step Size and Focusing points calculated.

Do you think my back plate is the built in tilt plate or is it just for collimation of the primary?

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  • 2 weeks later...
On 26/12/2018 at 12:59, Fellside said:

John,

The plain of my CCD is 247mm from the back plate. This maybe a little different on your scope as yours has a flat rear plate. TS quote 250mm for your scope. TS also state that removing 1 25mm spacer should bring the scope to focuse when using the focal reducer. I did not find this. So a little more experiment is required.

Hope this helps

Graham

Hi Graham,

 

If you have the tilt adaptor from TS for your RC10C you will not be able to reach focus even without any of the spacers. What I did to achieve focus was to move the CCD67 into the focuser tube (I used the RiredM63-M68 to connect to TSFOCR30S and placed the CCD67 in the focuser via the M48 female and added the necessary spacers on the camera side of the RiredM63-M68). 

I hope this will be helping someone with the same problem. 

Mihai

IMG_2858.jpg.5f5932e6cb7bf5bea814ca9ce0cbe90c.jpg

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Hi Mihai,

I've attached a pdf showing the backfocus of the AP reducer which they claim is 85mm, my train should just about accommodate it, the distance from my CCD to the front of my FW is 33.5mm, so with the backfocus at 85mm I have 51.5mm to play with, which should be just about perfect as long as my OAG is in front of the FR.

With 250mm being the total distance, then I shoudln't have any problems fitting it all in.

Teleskop-Express Astro Physics CCDT67 067x Reducer 2 - eg for GSO RC.pdf

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17 hours ago, mihaighita said:

Hi Graham,

 

If you have the tilt adaptor from TS for your RC10C you will not be able to reach focus even without any of the spacers. What I did to achieve focus was to move the CCD67 into the focuser tube (I used the RiredM63-M68 to connect to TSFOCR30S and placed the CCD67 in the focuser via the M48 female and added the necessary spacers on the camera side of the RiredM63-M68). 

I hope this will be helping someone with the same problem. 

Mihai

 

I have a similar setup for my 8" RC and it works well.  I have the TS focuser and the M68 to M48 adapter (also from TS).  As you say, the CCD67 screws onto the front of the adapter and then it sits inside the focuser.  I can get focus on my setup with or without the FR in place and do not have to add or remove any extension tubes.  If I recall correctly, the focuser has to be racked in about 4cm when the FR is installed.

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16 hours ago, Jkulin said:

Hi Mihai,

I've attached a pdf showing the backfocus of the AP reducer which they claim is 85mm, my train should just about accommodate it, the distance from my CCD to the front of my FW is 33.5mm, so with the backfocus at 85mm I have 51.5mm to play with, which should be just about perfect as long as my OAG is in front of the FR.

With 250mm being the total distance, then I shoudln't have any problems fitting it all in.

Teleskop-Express Astro Physics CCDT67 067x Reducer 2 - eg for GSO RC.pdf

Hi John, 

You should not have any problems with the truss RC as the tilting adaptor is integrated flush to the rear plane of the scope. I was referring to the steel/carbon tube that are coming without the tilt plate and that needs to be added afterward. On the steel tube RC the tilting flange is eating about 20 mm of the backfocus and with the CCD67 is not possible to reach focus if screwed after the focuser. You have another advantage in using the FT focuser that is a bit shorter than the TSFOCR30S focuser. In my config (10inch Steel Tube RC with tilting plate adaptor and TSFOCR30S) I ended up using the CCD67 and a 15mm extension tube inside the focuser to be able to reach focus. 

Mihai

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  • 2 weeks later...

I'm having major surgery on my spine next week and because of the atrocious weather I still had not had a chance to do any proper imaging, in fact I haven't done so since the 3rd week of October, I have never known such a long spell without proper clear nights ?

Anyway, I thought whilst I can than I had better have a play with the balance points and ease of use of fitting the OTA onto the mount, as more often than not for the next 3-6 months I will be reliant on family and friends to slide it on and off as I will be forbidden to lift anything during the period.

Now I'm about 5ft 10" and my pier is quite tall, deliberately so as I didn't want to be crouching under it for alignment and checking things, but I have to admit that even with a weak back, I had to use a bit of caution when sliding it on. I had drilled and mounted a 14" Losmandy bar, but as it turned out it was not needed and I have since reverted to the original 10" one that it came fitted with originally.

My son is 6ft 2" and built like a proverbial brick house, so he will have no problem, my weedy mate who is a similar height to me and has a very strange resemblance to a bald twiggy (isn't that right Mark @Toxophilus) ? may have to go on a body building course...lol, nah it's not that bad, but I did fit it without the camera, filter wheel which saved a few kilos.

Balancing was better than expected, I did need both 9.5kg weights and surprising the RA was fairly well balanced and will just need a minor adjustment because the rail has reverted to the original, the DEC will need a little more balancing, nothing that a few 25gm stainless steel washers can't resolve to counteract the focuser side, but otherwise I was quite impressed with the overall balance, it is a big beast though!

When I finally get a chance to image with it, providing Mr Twiggy doesn't drop it then will post up first light: -

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There's a slim possibility of some imaging on Sunday, but not with LRGB as we are fast approaching a full moon, so will stick to NB

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Hi John, it's looking very impressive . Looking forward to seeing some nice galaxy pics soon and of your opinion of the scope [as I am interested in these truss RC'S also]. Fingers crossed for Sunday night and early Monday morning.

I do hope all goes well with your surgery and you will be  up and running again soon. Please give my regards to Mark when you next see him.

All the very best,

                         Bob.

 

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  • 2 weeks later...

Well first light last night was a true testing night and first light as I never expected it to go clear, but I figured at about 21:00 that it would be clear enough to get my focusing points, OAG focus and G2V subs collected.

I have had the Scope over 6 weeks now and this was the first night that was clear enough to take advantage of.

It was the first time checking that everything was working and the first fault was some weird foibles with the focuser, it appeared that the Cat5 cable I made up had a fault and therefore intermittently failed to control the Pegasus focuser, so I quickly grabbed a cat 5 cable that I had in my laptop case and sure enough everything was working beautifully after that.

So first thing was to get the focus sorted so that i could then get the OAG in focus, by this time it was well after 01:00 in the morning and the temp recorded on my focuser was -6.1c but it didn't feel that cold.

I was particular keen to see what the collimation was like and how well the secondary dew heater worked.

Up until about 03:00 the seeing wasn't the best as there was still a few clouds passing over, but I managed a nice V curve with the luminance (thanks @RayD as your vids refreshed my memory on setting these up), but the RGB was not so lucky and I am really not sure why as the filters are parfocal being Chromas 50mm unmounted, and they had been fine with the Esprit 80 that I had first tested these on, so my only guess is the seeing unless anyone else has any thoughts?

V-Curve.JPG.938f41b57a3e96baf6fea462fd649b03.JPG

So you will have to excuse the messy cabling as I had to undo all of the cabling to check the cat5 cable.

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I used Sharp Cap for my Polar alignment and I have to admit it really is very good and IMHO far superior in speed and accuracy versus the Polemaster software.

I never expected to be able to grab anything of a sequence last night, but was quite pleased with this 10 min sub screen grab of M51, to me it looks like there is no collimation errors to worry about or tilt, but I may end up eating my words when I do some proper captures hopefully at the weekend.

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I did grab a quick 5 min sub of M101 just to be sure and looking closely at the stars it really does look like the optics are spot on as is the guiding. I deliberately captured it offset as I wanted to see how flat the image was.

M101.JPG.aa9b8d5f12bef930e3976dc9f2969ad8.JPG

So there you have it, hopefully we'll get finally some more clear skies and I can then put this 10" RC through its passes.

All the best.

NB BTW Bob, thanks for the good wishes, the Op was cancelled, was all in my gown and IV in and they cancelled because of health complications ? thus why I managed to do this as no spinal surgery!

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