RDF annoyances

[wibblefish]

1 minute ago, SuburbanMak said:

Looks business-like. After one night of rolling around on the floor getting neck-ache I went all-in on finders too. After a couple of sessions I can tell I am not going to regret a penny and sure you will find the same.  +1 on everything folk saying here about alignment, I got it as best I could on the top of a church spire about 500m away  then fine tuned on first the moon & then Capella in one of those rare clear nights, happy star-hopping!

Honestly even slightly poorly adjusted the finderscope is a brilliant upgrade, I appreciate my telescope is probably wide enough to be its own finder but still its making life a bit easier star finding and hopping which is what I was after - that and turning the diagonal back upright instead of the jaunty 90 angle it was at original *facepalm* 

[Dantooine]

28 minutes ago, wibblefish said:

I usually keep my glasses and torch on the tray but possibly a good plan. After an incident where an EP fell off the tray when repositioning the other week I got myself a fishermans tripod rest which I can just plonk the EPs I am swapping in and out in, seems to be fine so far with my little collection of BSTs though probably not a good place to put to much weight  

I think I’d keep bst’s  in my coat pocket. Just the right size. One in the focuser, 1 left pocket, 1 right pocket. Nice and organised 😁

[Pixies]

55 minutes ago, wibblefish said:

I usually keep my glasses and torch on the tray but possibly a good plan. After an incident where an EP fell off the tray when repositioning the other week I got myself a fishermans tripod rest which I can just plonk the EPs I am swapping in and out in, seems to be fine so far with my little collection of BSTs though probably not a good place to put to much weight  

I used to place my EP case on a little camping table and keep it near me when observing. But recently, I stick mainly with my widefield plus a zoom at the scope and if I decide to use a prime EP or get a filter, I wander off to the back door and grab them from there.

[wibblefish]

8 minutes ago, Pixies said:

I used to place my EP case on a little camping table and keep it near me when observing. But recently, I stick mainly with my widefield plus a zoom at the scope and if I decide to use a prime EP or get a filter, I wander off to the back door and grab them from there.

Honestly I am just being lazy instead of walking over the garden to the case that they normally sit in which I put on a chair where I keep my books / notepad but I have found chasing doubles recently at different mags having the 3 EP + barlow to hand makes life easier

Edited February 4, 2021 by wibblefish

[Pixies]

1 minute ago, wibblefish said:

Honestly I am just being lazy instead of walking over the garden to the case that they normally sit in which I put on a chair where I keep my books / notepad but I have found chasing doubles recently at different mags having the 3 EP + barlow to hand makes life easier

It's only a matter of time.........

 

Zoom

[Louis D]

On 31/01/2021 at 17:30, Dantooine said:

I’m surprised nobody’s mentioned laser finders. 

 

On 31/01/2021 at 17:40, JeremyS said:

What about laser finders? 🤣

Yeah, there seems to be a general aversion to them on SGL as compared to CN.  I love my cheapo ebay laser sights.  One is permanently mounted on a Picatinny rail on my Dob while another is on a Vixen/Synta finder foot to Picatinny rail adapter for use on the refractors.  I even have one permanently mounted on my DSV-1 mount's handle via the barrel adapter that comes with them.  I still keep a Telrad or Rigel mounted for when the rechargeable battery goes south during an observing session.  Lasers are great for those of us with neck and back injuries.  They also rule for use near zenith.  There's also no debate about using them with one eye or two eyes open.

[Dantooine]

9 minutes ago, Louis D said:

 

Yeah, there seems to be a general aversion to them on SGL as compared to CN.  I love my cheapo ebay laser sights.  One is permanently mounted on a Picatinny rail on my Dob while another is on a Vixen/Synta finder foot to Picatinny rail adapter for use on the refractors.  I even have one permanently mounted on my DSV-1 mount's handle via the barrel adapter that comes with them.  I still keep a Telrad or Rigel mounted for when the rechargeable battery goes south during an observing session.  Lasers are great for those of us with neck and back injuries.  They also rule for use near zenith.  There's also no debate about using them with one eye or two eyes open.

I think lasers on telescopes in the Uk is shortly followed by a visit from the police helicopter 😂

[Tiny Clanger]

3 hours ago, Dantooine said:

I think I’d keep bst’s  in my coat pocket. Just the right size. One in the focuser, 1 left pocket, 1 right pocket. Nice and organised 😁

I have electronic level in left coat pocket, little red torch and tissue ( runny nose in the cold for the use of) in the right. 

EPs go in a repurposed small padded camera accessory bag with home bodged BST sized compartments of closed cell foam on a waist belt . Keeps the EPs safe and warm, and less likely to encounter whatever debris my pockets have acquired . Also I don't forget where I  put them, or kick the table over , or trip over the cat while moving to fetch them, or forget which is which ... set order, ranked by mm , lowest to the right, returned religiously to the same compartment to avoid faff.

I don't like faff, it wastes time !

 

 

[Tiny Clanger]

6 hours ago, wibblefish said:

Thanks for the tips, alas seeing anything about a mile away is pretty much a no-go during the day (I usually use a chimney on a house over the road) and since it seems like night is best to align the Rigel I may as well do the finder then on something bright as well it'll give me something to do at the beginning of next session no doubt

Interesting, I didn't think of that, might have to have a look at doing that in the summer when we refill the kiddos sand pits  

I even have some old ankle weights around maybe I'll just wrap them around the tripod legs.

Adding a weight to a tripod to make it more stable  is a well known photographers trick : there are bags made for the purpose (similar to your anglers one )

https://www.amazon.co.uk/Neewer®-Photographic-SandBag-Manfrotto-Universal/dp/B01E5350TI

But a length of string tied somewhere near the tripods centre, with a 2 litre bottle of water hung off it   is cost effective and works pretty well too 🙂

 

[AlexK]

Re optical finder alignment.
Surely the best alignment target is Polaris (or any other bright star when you learn to work fast to ignore the celestial drift). However, terrestrial targets can be totally adequate if you simply adjust the process for the parallax. In a nutshell, after pointing the telescope to a feature on a terrestrial target (e.g. a corner of the brick on the mentioned above chimney) point the finder away from that feature with an offset equal to the offset and direction of these two optical axes difference as if they are drawn on that chimney (surely you should know the brick and gap size, but a sane estimation is usually enough). That's also the way to figure if aligning on a particular terrestrial target needs any adjustment at all (if the needed offset is impossible to figure looking through the finder, that means there is no adjustment for the parallax required at all).

Another crucial consideration should be made for the actual pointing technique with a particular optical finder. The crosshairs in various models are different in features so no universal advice (the cross' thickness, orientation, subtle crosshairs manufacturing features you could leverage...). E.g. on my 8x50 RACI the cross is enormouslysly thick, so stars are passing behind it for like a minute. That means you can't actually point with it precisely enough to always hit the target with a high mag narrow AFOV EP. The common advice is to point with low mag EP first to amend these issues, but that adds other issues for a novice (overcrowded FOV). However, instead of guess-centering the cross over the target and then hoping that semi-bright star on the edge of the FOV is what you are centering, you can point much more accurately with the particular cross' corner instead. E.g. the topmost one (on my 8x50 I simply disassembled the EP, scratched the paint on one of the cross lines near the center with a needle, and got a decent sharp point in it to align with targets much more accurately, that's especially useful on mine as it's easy to rotate in the holder so I'm often using that feature for outreach for manual planets guiding standing on the other side of my Dob at the finder EP with the guest at the main EP to avoid us jumping around; despite the huge magnification difference it works tolerably even at 200x ).

Also, keep in mind that optical finders might have a significant parallax as well in case the cross and the target are not in perfect focus. Cheap finders often have a focuser for the objects, but nothing for the crosshairs. So when focusing the finder focus your eye on the cross first, then focus stars keeping the cross focused. In a worst case (no way to bring both into the same focus plane and eyeglasses are not an option) use the "eyeballing" technique to amend that to some extent: Center your focused star on the crosshairs and now move your head around a bit so the eye looks through the EP at the crosshairs at different angles. You will see it moving around the star. That's the parallax due to difference in their focal planes. The idea is to find the center of that circle, stop "eyeballing" at that center of it and move the scope so the target star is under the crosshairs there.

And finally, the tip for the scope alignment accuracy improvement using a bright star: Just defocus it. The eye is much better distinguishing the perfect concentricity than the perfect centrality. So having the alignment star in the eyepiece view looking like a large disk (donut in a reflector) it will be much easier to ensure the telescope is perfectly centered on the star by keeping its edge concentric (equally spaced) with the EP field stop (warning! not working with 100 deg AFOV EPs well ). The same can be used with the optical finder, but instead of concentricity watch for the defocused disk to be equally split by the cross, as some crosses might be not exactly centered in the FOV (surely only if your finder is easy to refocus as some are easy to knock off from just trying that).

By the way, the "by the crosslines feature" pointing technique above is applicable to ordinary RDFs too, as they often having an irregular red dot. E.g. I once had an RDF which dot looked like a tiny angled stick (narrow ellipse actually). No biggie, even beneficial as I found pointing by placing targets on its sharp top end highly accurate. Telrad, QuInsight, and Rigel obviously much better at that as they have a tiny ring helping to center stars ideally by concentricity and without obstruction (just watch for the parallax error compensated by "eyeballing" if it's significant in your device).

Edited February 5, 2021 by AlexK

[Kimboman]

Thanks for the information I will look into obtaining the same type of rdf cheers and clear skys

 

[AlexK]

11 hours ago, Louis D said:

Yeah, there seems to be a general aversion to them on SGL as compared to CN.

Simple. UK and EU have an International airport like in every neighborhood, and it's hard to tell when one neighborhood ends and another starts. Few thousands years of development are incomparable with just a few hundreds in the US 

[CRAZYeye29325]

On 31/01/2021 at 17:27, AlexK said:

Sure thing, go ahead. That's just cheap me. Though you can trust me on one thing: it's no different (and actually worse due to its miniscule aperture, impossible to reach for wiping) than my 20 years old $5 shipped off eBay from China RDF which is still kicking even on my 12ga shotgun (these are sold for ~$35 nowadays):

 

Seriously. Just make sure you can return that nonsense. For $400 you can get an amazing Nitrogen filled true-zero-parallax internally alignable holographic gunsight:



But I'd rather get another 100 deg EP for that money.

OMG, is that a Palm Pilot?