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Old 16-10-2019, 11:46 AM
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Bluknghtv (Daniel)
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MMM decisions, edge 8 or 9.25

Bit of a dilemma regarding these two scopes. 230mm focal difference compared to the cost difference. Wanting this second scope for galaxy season once my azeq6 gt comes back from being super tuned.
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Old 16-10-2019, 12:44 PM
Startrek (Martin)
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Daniel
Your cameras pixel pitch ( uM) should have a bearing on what scope you choose especially in Bortle 3 skies down the south coast
General rule of thumb for image or pixel scale is aim for 1 to 2 arc sec per pixel. Iím imaging at around 0.90 with my newts which is slightly over sampled but works well at Sydney and better at Narrawallee
As far as Aperture goes an 8Ē should be large enough as Iím imaging up to magnitude 9.5 galaxies at Narrawallee with my 8Ē f5 newt at only 1000mm focal length
You want to get your image scale closer to 1.0 arc sec per pixel to take advantage of those beautiful dark skies down there
Cheers
Martin
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Old 16-10-2019, 05:11 PM
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Bluknghtv (Daniel)
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yeah mate, I have been going onto bintel site and trying to figure out the mag with what scope for my canon 5dsr. my eon f7 doesn't get close enough for those smaller galaxies such as the superman etc. I want to capture the not so known ones which aren't photographed a lot

going off the FOV calculator even the edge c8 would suit the 5dsr, even better with the zwo 1600. The money I save on the c8 I could go to the zwo route for the main camera

http://www.12dstring.me.uk/fovcalc.php
view with the 8" quatro 1.06"/pixel. Like to get closer but I need to remember though the pixelation in over and under sampling when enlarging the photos

Last edited by RB; 16-10-2019 at 06:48 PM.
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Old 16-10-2019, 08:10 PM
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Camelopardalis (Dunk)
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How about an 8” f/5 newt? Or if you want a little more focal length, the 10”?

Easier to collimate than the f/4 scope, but still substantially faster than the Edge scopes (f/10).
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Old 16-10-2019, 08:16 PM
Wavytone (Nick)
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Daniel the same focal ratio, and a difference between the two of a mere 15% in aperture/focal ratio and 33% in light-grasp. Not a significant difference.

Changing the parameters by a factor of 2 is where it gets interesting - focal ratio, aperture or focal length.

Hence I’d say look for an 8” f4 or 5 Newtonian, or a 190 mm Maksutov Newtonian (Skywatcher and Orion made some suitable for imaging). The latter are rare but do work well, occasionally one appears secondhand.
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Old 16-10-2019, 08:16 PM
Startrek (Martin)
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A Canon 5dsr has a full frame sensor which will be to wide for a 2Ē crayford focuser. APS-C crop sensors are more suitable for 2Ē focusers

FOV calculator ( in arc minutes )
Width or Height of camera chip in mm x 3460 / telescope focal length in mm

Cheers
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Old 16-10-2019, 08:17 PM
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Bluknghtv (Daniel)
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yeah I'm looking at the sky watcher quatro's. There is also the saxon 254 newt but don't know much about the saxons
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Old 16-10-2019, 09:24 PM
Startrek (Martin)
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Are you aware that f4 Astro newts like the Quattro in 8Ē and 10Ē can be difficult to collimate and keep collimation if moved off and on a mount regularly ie: moved around a bit
Thatís why I went for an f5 they are more forgiving in regards to collimation , I check mine once in a while for collimation and normally they donít require adjustment
Saxon telescopes are marketed from NZ but are made you guessed it ( in China ) like everything else
Skywatcher scopes have had a good name world wide for many years ( also made in China ) but very good support in Australia
Bintel GSO scopes are slightly cheaper ( made in Taiwan ) and have good optics and in my opinion better dual speed focusers than Skywatcher ( also good support in Australia via Bintel )
I have both Skywatcher and Bintel scopes and mounts , so you canít go wrong with either
My advice, do your research on the f4 astrographs !!
My 2 cents ......
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Old 16-10-2019, 11:16 PM
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yep heard about the f4's. I am quite keen on a 190 mak newt as mentioned by Wavytone but focal length isn't much different to my eon 130. the 190 1000mm, eon 910mm but the 190 is at f5.3
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  #10  
Old 17-10-2019, 05:19 AM
Startrek (Martin)
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Have you considered a Sidereal Trading 10Ē f5 carbon fibre newt
Huge aperture, long focal length at 1250mm , easy to collimate and light enough on your big AZ Alt mount
A real galaxy hunter down there
Only one caveat, on a windy night , guiding will be affected but I use poly tarps from Bunnings and hook them up on some small trees around my 8Ē f5 when Iím at Narrawallee and itís windy and have managed to guide under 1 arc sec in 25 km/hr whilst imaging galaxies
Attached image of Pavo Galaxy on a windy night at Narrawallee with my 8Ē f5 newt
Just a thought !
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Click for full-size image (41FD8BB5-C466-498A-BD5C-0E4AD0EA01D7.jpg)
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  #11  
Old 17-10-2019, 07:26 AM
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Bluknghtv (Daniel)
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thanks for the info Martin I will have another look at the sidereal. That was the other thing I read about was the wind problem but I figure at most if the wind is blowing it generally caused turbulence higher up anyway so I don't worry about shooting. As you would know though the August winds usually blow down here
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Old 17-10-2019, 07:34 AM
Startrek (Martin)
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The wind, turbulence or jetstream up high doesnít worry us too much , you can live with that , itís the wind on the ground that really affects your guiding and therefore ruin your images , guiding is so sensitive to any subtle movement
Have you guided before ?
If not myself and most other members will thoroughly recommend PHD2 , itís free software
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Old 17-10-2019, 08:57 AM
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Bluknghtv (Daniel)
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yeah mate I only photograph, very rarely observe. I've got phd2 and use it but wanted my mount to be alot better hence sending it over the WA to get supertuned so won't have it for about 2 weeks. I think I have decided now on my set up, the sidereal 250 DS ota and the zwo asi294pro colour. the sampling with this using the 250 and my eon 130 refractor is quite good anywhere from .8 to 1.06. A bit over sampling if using 1.5x powermate etc. I may get a moonlite focuser for it also
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Old 17-10-2019, 09:02 AM
Startrek (Martin)
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Good choice for chasing those faint fuzzies
I use a JMI moto focus with 2m cord and handcontroller, not as sophisticated at other autofocusers but itís super light , easy to use and does a good job, always trying to save payload weight
Good luck and enjoy !!
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Old 17-10-2019, 09:11 AM
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Bluknghtv (Daniel)
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How do you find dew build up though. I get a fair bit here in the back yard being so close to the beach. Not sure how to set up the dew strap if needed for the secondary. I already use the kendrick for my eon so it would be just a bigger strap. Highpoint scientific sell secondary heat guards but they don't ship to oz
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Old 17-10-2019, 09:37 AM
Startrek (Martin)
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Yeah dew can finish your night early, where ever you Image
I use Kendrick dew straps on everything with an Orion 4 channel dew zapper controller
Itís set up each session regardless , only takes 5 minutes or so but can save your night
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Old 17-10-2019, 09:42 AM
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el_draco (Rom)
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Dirt cheap OTA in Classifieds ATM....:-)
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  #18  
Old 18-10-2019, 08:04 AM
Startrek (Martin)
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Daniel
Just wondering where you sent your mount to in WA to get hyper tuned ?
And what does it entail
Cheers
Martin
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