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I'm looking for a lightweight inexpensive refractor that has at least a 400mm focal length to use as a guide scope that weighs less than my ST80. The SVBony 501P 70mm F/5.7 seems to fit the bill. The complete weight including tripod and backpack that it comes with is 4 pounds so I can imagine the tube weight being probably no more than half that since the tripod is made of aluminum, I've posted the question to the manufacturer and will update if they answer. The focuser is a 1.25-inch draw tube and has a 42mm standard thread for a T-adapter, though that is not necessary for my application, it's a nice feature. The objective is 2 elements in 2 groups and multi coated for high transmission. The camera would be an ASI120 or 290. Only issue I see is dew because the tube is made of plastic. The 60mm version would weigh even less but it's F/6.3
Anyone have or used this scope? Thoughts about its use as a guide scope?
I'm sure it will work just fine. I found my guide scope from the local classifieds for 10 bucks so if that works then this scope should have no issues.
The one feature you would like to have is a way to lock the focuser. Locking the focuser is nice because it eliminates image shift by the focusing tube moving within the focuser housing.
∞ Primary Scopes: #1: Celestron CPC1100 #2: 8" f/7.5 Dob #3: CR150HD f/8 6" frac ∞ AP Scopes: #1: TPO 6" f/9 RC #2: ES 102 f/7 APO #3: ES 80mm f/6 APO ∞ G&G Scopes: #1: Meade 102mm f/7.8 #2: Bresser 102mm f/4.5 ∞ Guide Scopes: 70 & 80mm fracs -- The El Cheapo Bros. ∞ Mounts: iOptron CEM70AG, SW EQ6R, Celestron AVX, SLT & GT (Alt-Az), Meade DS2000 ∞ Cameras: #1: ZWO ASI294MC Pro #2: 662MC #3: 120MC, Canon T3i, Orion SSAG, WYZE Cam3 ∞ Binos: 10X50,11X70,15X70, 25X100 ∞ AP Gear: ZWO EAF and mini EFW and the Optolong L-eXteme filter ∞ EPs: ES 2": 21mm 100° & 30mm 82° Pentax XW: 7, 10, 14, & 20mm 70°
Searching the skies since 1966. "I never met a scope I didn't want to keep."
JayTee wrote: ↑Thu Feb 16, 2023 2:05 am
I'm sure it will work just fine. I found my guide scope from the local classifieds for 10 bucks so if that works then this scope should have no issues.
The one feature you would like to have is a way to lock the focuser. Locking the focuser is nice because it eliminates image shift by the focusing tube moving within the focuser housing.
Thanks, I thought as much but liked confirmation, I still feel new at times. It has a twist screw on top of the focuser draw tube, cool. This will be a nice upgrade.
Weight has really become an issue on the EQ6. I sat down tonight and added it all up by the ounce, my ratio is at 77%, didn't think it added up quite that much. I had it out a couple nights back and guiding was not the greatest, chocked it up to average seeing that turned poor. Could see wispy clouds in PHD2 in my clear skies with above average transparency. Hope to try again this weekend. Curios to see how it will perform with that load with all around decent skies.
Image Cam: Canon 6D (Ha mod), 600D (Stock), SVBony SV405CC
Image OTA: EvoStar ED80, WO Z73, C8-A XLT
Mount: EQ6-R Pro Pier, AZ-EQ5 Pro Pier
Guide OTA: Orion 60mm, WO 32mm, ZWO OAG, SV501P
Guide Cam: ZWO 120mm, 290mm mini
EAA OTA: Orion ST80
EAA Cam: SVBony SV705C
EP: Baader Hyperion Modular Set
Filters: L-Pro Canon EOS C, L-eNhance, L-Pro, Optolong Ha 7mm, Optolong Oiii 6.5mm, Optolong Sii 6.5mm, ES H-Beta
Session Control: Mini PC/Win11 Pro, APT 4.1, PHD2 2.6.10
Processing: PixInsight, DSS 4.2.6, Adobe PS CC, Astronomy Tools Action Set, Star Spikes Pro
My guide scopes cost about the same as JT's scope. I bought mine from Yahoo auction. Both have 60mm objective lenses with 420mm focal lengths and they are both achromats. I drilled and tapped locking screws in them both. They are working with no issues at all. You don't need to spend mega bucks on a guide scope. Just make sure it's solidly mounted and the image scales between your guide scope and imaging scope are close. My main imaging setup image/guide ratio is 1:077 which works great even with a relatively rough polar alignment. Some recommend no more than 1:4, Personally, I don't go any higher than 1:2. But, it depends on your focal lengths, pixel pitch and physical limitations.
You can use this site to find a suitable setup. https://astronomy.tools/calculators/gui ... uitability Just adjust the values until you find something that gets you within a ratio that's desirable and meets your physical needs.
Arry (Bortle 7 area)
Telescopes: Sky-Watcher ED72II, Sky-Watcher PDS130, Sky-Explorer SN F4 200mm astrograph and Vixen F11.1 90mm Cameras: Nikon D5300 modded, Canon Kiss X8i modded, Cooled Canon kiss X4 modded, Atik 16IC and 383 colour, ASI120MC, QHY5LII Mount: Sky-Explorer HEQ 5 belt driven
Gmetric wrote: ↑Thu Feb 16, 2023 5:16 am
My guide scopes cost about the same as JT's scope. I bought mine from Yahoo auction. Both have 60mm objective lenses with 420mm focal lengths and they are both achromats. I drilled and tapped locking screws in them both. They are working with no issues at all. You don't need to spend mega bucks on a guide scope. Just make sure it's solidly mounted and the image scales between your guide scope and imaging scope are close. My main imaging setup image/guide ratio is 1:077 which works great even with a relatively rough polar alignment. Some recommend no more than 1:4, Personally, I don't go any higher than 1:2. But, it depends on your focal lengths, pixel pitch and physical limitations.
You can use this site to find a suitable setup. https://astronomy.tools/calculators/gui ... uitability Just adjust the values until you find something that gets you within a ratio that's desirable and meets your physical needs.
Thank you for the link, that scope's ratio to my C8 is 1.2 at 1280 and 1.318 at 2032. It also opens up my thought process to adding a Barlow to the guide scope later, if that would improve guiding.
Clear Skies,
Chris
Image Cam: Canon 6D (Ha mod), 600D (Stock), SVBony SV405CC
Image OTA: EvoStar ED80, WO Z73, C8-A XLT
Mount: EQ6-R Pro Pier, AZ-EQ5 Pro Pier
Guide OTA: Orion 60mm, WO 32mm, ZWO OAG, SV501P
Guide Cam: ZWO 120mm, 290mm mini
EAA OTA: Orion ST80
EAA Cam: SVBony SV705C
EP: Baader Hyperion Modular Set
Filters: L-Pro Canon EOS C, L-eNhance, L-Pro, Optolong Ha 7mm, Optolong Oiii 6.5mm, Optolong Sii 6.5mm, ES H-Beta
Session Control: Mini PC/Win11 Pro, APT 4.1, PHD2 2.6.10
Processing: PixInsight, DSS 4.2.6, Adobe PS CC, Astronomy Tools Action Set, Star Spikes Pro
Just got an answer on the weight of the OTA by itself, .45kg, 1 pound! That change alone would change the weight ratio from 77% to 71% And the planned PC upgrade will take the ratio to 53.84 if I remove the Primaluce saddle plate and use Velcro instead to secure the new PC to the rail.
Wow, no reason not to do this when some funds become available for upgrades.
Cler Skies,
Chris
Image Cam: Canon 6D (Ha mod), 600D (Stock), SVBony SV405CC
Image OTA: EvoStar ED80, WO Z73, C8-A XLT
Mount: EQ6-R Pro Pier, AZ-EQ5 Pro Pier
Guide OTA: Orion 60mm, WO 32mm, ZWO OAG, SV501P
Guide Cam: ZWO 120mm, 290mm mini
EAA OTA: Orion ST80
EAA Cam: SVBony SV705C
EP: Baader Hyperion Modular Set
Filters: L-Pro Canon EOS C, L-eNhance, L-Pro, Optolong Ha 7mm, Optolong Oiii 6.5mm, Optolong Sii 6.5mm, ES H-Beta
Session Control: Mini PC/Win11 Pro, APT 4.1, PHD2 2.6.10
Processing: PixInsight, DSS 4.2.6, Adobe PS CC, Astronomy Tools Action Set, Star Spikes Pro
chris_g wrote: ↑Thu Feb 16, 2023 5:12 pm
Adding a Barlow to the guide scope later, if that would improve guiding.
PHD2 can effectively guide at 1/10 of a pixel. Of course if you're mount can't do that then PHD2 is guiding better than your amount can provide. Using a barlow in most cases is unnecessary. You're introducing a new optical surface, actually two of them, and it's another mechanism to move, or get misaligned, or whatever giving you potential headaches.
∞ Primary Scopes: #1: Celestron CPC1100 #2: 8" f/7.5 Dob #3: CR150HD f/8 6" frac ∞ AP Scopes: #1: TPO 6" f/9 RC #2: ES 102 f/7 APO #3: ES 80mm f/6 APO ∞ G&G Scopes: #1: Meade 102mm f/7.8 #2: Bresser 102mm f/4.5 ∞ Guide Scopes: 70 & 80mm fracs -- The El Cheapo Bros. ∞ Mounts: iOptron CEM70AG, SW EQ6R, Celestron AVX, SLT & GT (Alt-Az), Meade DS2000 ∞ Cameras: #1: ZWO ASI294MC Pro #2: 662MC #3: 120MC, Canon T3i, Orion SSAG, WYZE Cam3 ∞ Binos: 10X50,11X70,15X70, 25X100 ∞ AP Gear: ZWO EAF and mini EFW and the Optolong L-eXteme filter ∞ EPs: ES 2": 21mm 100° & 30mm 82° Pentax XW: 7, 10, 14, & 20mm 70°
Searching the skies since 1966. "I never met a scope I didn't want to keep."
chris_g wrote: ↑Thu Feb 16, 2023 5:12 pm
Adding a Barlow to the guide scope later, if that would improve guiding.
PHD2 can effectively guide at 1/10 of a pixel. Of course if you're mount can't do that then PHD2 is guiding better than your amount can provide. Using a barlow in most cases is unnecessary. You're introducing a new optical surface, actually two of them, and it's another mechanism to move, or get misaligned, or whatever giving you potential headaches.
Thank you, I have a lot to learn about optics...
Image Cam: Canon 6D (Ha mod), 600D (Stock), SVBony SV405CC
Image OTA: EvoStar ED80, WO Z73, C8-A XLT
Mount: EQ6-R Pro Pier, AZ-EQ5 Pro Pier
Guide OTA: Orion 60mm, WO 32mm, ZWO OAG, SV501P
Guide Cam: ZWO 120mm, 290mm mini
EAA OTA: Orion ST80
EAA Cam: SVBony SV705C
EP: Baader Hyperion Modular Set
Filters: L-Pro Canon EOS C, L-eNhance, L-Pro, Optolong Ha 7mm, Optolong Oiii 6.5mm, Optolong Sii 6.5mm, ES H-Beta
Session Control: Mini PC/Win11 Pro, APT 4.1, PHD2 2.6.10
Processing: PixInsight, DSS 4.2.6, Adobe PS CC, Astronomy Tools Action Set, Star Spikes Pro