Sunday, January 31, 2021

Orion 70mm Multi-Use Finder Scope

Just would like to share my impressions with this simple purchase.



At $100 it's somewhat overpriced for what it is indeed, as at the close inspection I have figured it's just the front piece of the Orion's 70mm binoculars plus the 6 adjustment screws shoe mount stalk and some threaded adapters. But overall it might worth it in the long run.

(the writeup is under construction)

Surely I have immediately rigged it for a correct image refractor utilizing a cheap China refractor's erecting prism I had laying around for eons, and an ancient (~1985) 25mm Russian TAL plossl eyepiece. 


To fit the latter I had to print the eyepiece adapter for the prism (orange) as the range of 7220 OTA focuser was insufficient with the stock EP tube and that TAL is actually about 0.5mm larger than the standard 1.25" EP barrel size so wouldn't fit the stock. Pictured is my quick setup on the photo tripod (been testing some ideas with pointing using the SkEye and DSO Planner apps with it).

On a side note. I have ordered a cheap CI 90 deg diagonal for it as well but it turned out to be far inferior to that 45 deg CI prism above I had shipped over a decade ago from eBay China along with the $25 80mm "toy" refractor on the table tripod. China is obviously on the rush for profit not for quality lately.

The 45 deg prism is way more appealing to me, compared to typical 90 dg used in RACI finders as when I'm looking through the eyepiece with the right eye, the left eye can be used for naked eye pointing.

Overall I like it sitting on my OTA:

<image on the OTA>

Even though I don't use optical finder in my pointing routine, relying solely on the QuInsight, it's adding the nice mounted ultra-wide FOV view to my z12. Yet to try it in the rural darkness with 100 deg EPs.

Specs

  • Objective diameter is 70mm
  • Focal length: 279mm
  • Focal ratio: f/3.9
  • Coatings: Fully coated
  • Glass material: Crown/Flint
  • Resolving power: 1.70arc*sec
  • Lowest useful magnification: 10x (stated, in fact 70mm/6mm ~12x)
  • Length: 8.2" (without eyepieces)
  • Weight: 1.2 lbs. = 544g (without eyepieces)

Pros

  • Quality is great.
  • Views are great.
  • Very lightweight.
  • The discrete mounting point is great for saving space on the UTA.
  • The possibility to change EPs on the RACI finder form-factor is useful.
  • Plenty of threaded adapters included for tinkering with various projects.

Cons:

  • The short close focusing range may not work with some diagonals.
  • The focusing range will require additional back extension for some EPs and diagonals.
  • Noticeably heavier than the standard 8x50

Ideas:

  • Rig with old 50mm binoculars using its "standard binos" thread.
  • Design a custom mount point to use it in tandem with the QuInsight.
  • Try with the DSLR.

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