RDF annoyances

[KP82]

1 hour ago, wibblefish said:

My telescope is an Evostar 90/660   (f7.3) short tube refractor. I dont have any knowledge for comparison but I am quite happy with it so far, a little soft at the edges but not enough to worry me. It works well as a grab and go out rather than having to faff to much. I should probably write a review eventually as I have not seen anyone mention this scope anywhere online but I guess thays fairly standard for a random beginner level telescope 🧙‍♂️

I had a scope with the exact same spec before, but it was sold under Celestron instead. I bought it off cheap (£60) from someone on UKAstroBuySell who was moving house and wanted to clear out some un-used stuff. The scope was in very good condition along with the stock Alt-az mount. There was also an audio gadget that was part of the original package, but the seller couldn't find it anymore.

I used it briefly before gave it to a friend and his 6 years old son who were both interested in stargazing. The performance was decent but the amount of CA was quite noticeable (expected from a fast achro).

Edited January 13, 2021 by KP82

[wibblefish]

57 minutes ago, KP82 said:

I had a scope with the exact same spec before, but it was sold under Celestron instead. I bought it off cheap (£60) from someone on UKAstroBuySell who was moving house and wanted to clear out some un-used stuff. The scope was in very good condition along with the stock Alt-az mount. There was also an audio gadget that was part of the original package, but the seller couldn't find it anymore.

I used it briefly before gave it to a friend and his 6 years old son who were both interested in stargazing. The performance was decent but the amount of CA was quite noticeable (expected from a fast achro).

I guess I haven’t had it long enough / got the experience to have spotted the effect of CA on what I am looking at for it ti annoy me. I am probably so busy going wowwee and hunting for various things to see any the moment 😀

I do keep an eye out for reviews though as its always interesting to see what people who have more experience make of things.

 

 

 

Edited January 13, 2021 by wibblefish

[Tiny Clanger]

5 minutes ago, wibblefish said:

I guess I haven’t had it long enough / got the experience to have spotted the effect of CA on what I am looking at. I am probably so busy going wowwee and hunting for various things to see any the moment 😀

I do keep an eye out for reviews though as its always interesting to see what people who have more experience make of things.

 

 

 

Going wowee is what it's all about !

The 25mm BST , directly compared with the stock 25mm , is worth what you pay for it in my opinion . Mind you , I bought mine second hand on here from someone called KP82 ... 😀

[Pixies]

2 hours ago, wibblefish said:

my scope is a bit “soft” towards the edges I think  mostly due to being a short tube so it doesn’t bother me to much.

I am kinda hoping the RACI will help me when (like last night in certain directions) I had periods where I was just placing the dot roughly where I thought the object was as the sky as it was just purple with no stars I could see to start hopping off from. When viewed through the binos I had no issues finding stars to guide, I did a lot of sweeping to with the 25mm and then switching to the 18mm when on target which was good fun and will likely do that until I sort a finderscope.

My telescope is an Evostar 90/660   (f7.3) short tube refractor. I dont have any knowledge for comparison but I am quite happy with it so far, a little soft at the edges but not enough to worry me. It works well as a grab and go out rather than having to faff to much. I should probably write a review eventually as I have not seen anyone mention this scope anywhere online but I guess thays fairly standard for a random beginner level telescope 🧙‍♂️

It might not be the scope that's making the outside stars soft. The 18mm BST does that with my f6 reflector, but the 12mm is dead sharp to the edge. Hopefully yours will prove to be the same.

Also, next time you see soft stars at the edge, adjust the focus slightly and see whether you can get the outside stars sharp (with out-of-focus at the inside). If you can, this is called field-curvature and is more associated with refractors. Basically, the focal-plane of the scope is not flat, so it's hard to get the whole field of view in focus at the same time. Some eyepieces handle this better than others. 

I have a RACI and it makes star-hopping loads easier, especially as your view will match the chart/app. You will find, however, that a RACI alone makes it tricky to align with your initial target. You might have to keep a non-magnifying finder attached. Other RACI/Refractor users might be able to comment?

[AlexK]

With a short frac in bright Bortles, I believe you just need to invest into the widest field (preferably over 100 deg AFOV) EP and practice the star hopping with good handheld digital star chart. When you can have the properly configured star chart view frankly side by side with the eyepiece view and a finger flick sync, it quickly becomes a second nature. So you will recall RDF and RACI times like a nightmare  I do. All the way to looking with one eye through the EP and with another on the screen.

Edited January 13, 2021 by AlexK

[AlexK]

In addition, as far as I have mentioned a smartphone, I must mention the Celestron Starsense Explorer (CSSE) modern marvel. But so far it means you have to buy their telescope first . Then move its phone cradle to your telescope.

If you never heard about it, in a nutshell, it allows to point a telescope to any invisible target in the sky using your smartphone (its photo camera and accelerometers sensors), and the guide for moving you scope by hands on the screen of the phone. Very similar to the Push-To flow, just 100% guaranteed landing on your target.

Edited January 13, 2021 by AlexK

[wibblefish]

@Tiny Clanger Yes, I had read a few reports that the 25mm is not that great but honestly at my skill level I can't discern any issues and its such an improvement over my existing stock 25mm in terms of clarity, field of view, eye relief (especially - omg!) that I am quite happy with it. 

@Pixies Ah I had read that actually now I come to think about it but didn't quite know how to test it, I will have a play with the focus and the EP the next time (in the far future!) that I am out and see. I presume its one of those trade offs that you get for having a short tube (much like every type of telescope from what I read!)  I intend to mount an RACI and a Rigel eventually (or perhaps just move the red dot which is likely my first plan).

@AlexK I am sure I will get there eventually, learning curve for the newbie :D, I currently use a combination of binoculars, RDF, phone app and some books to identify targets in the sky! The binoculars are quite a lot more useful especially when the sky is just a purple haze at points in the evening (or if I get blinded by the various street lights / neighbours security lights/ neighbours bright kitchen and bedroom lights lol) which makes trying to find anything to aim the RDF at a complete nightmare! Interesting about the phone holder thing, I do often actually place the phone directly behind the tube to try and ascertain if the target is vaguely in the right direction!

Edited January 14, 2021 by wibblefish

[wibblefish]

I really appreciate all the replies and information everyone is chipping in with its really helpful! This is a great forum and I just hope I can pay it forward as I get more experience

[Zermelo]

On 12/01/2021 at 14:16, Zermelo said:

If you're looking at the Skywatcher 6x30 RACI, the figure I found was 308g including the bracket?  I'll find out soon - mine is due imminently

@wibblefish, my SW 6x30 finally arrived today, and is actually only 257g including the bracket.
I've no idea where I got my other figure from, but losing 50g is a bonus.

[wibblefish]

43 minutes ago, Zermelo said:

@wibblefish, my SW 6x30 finally arrived today, and is actually only 257g including the bracket.
I've no idea where I got my other figure from, but losing 50g is a bonus.

Thanks for the update, less weight is good! I think I will likely persevere with the RDF for now (maybe move it further towards the nose of the telescope) and then look to get the 6x30 RACI and a Rigel as soon as I have some spare pennies (not that anywhere will be delivering them any time soon!)  Annoyingly I will probably have to source the Rigel from FLO and then get the RACI from somewhere else as nowhere seems to do both!

Edited January 14, 2021 by wibblefish

[Louis D]

23 hours ago, AlexK said:

n addition, as far as I have mentioned a smartphone, I must mention the Celestron Starsense Explorer (CSSE) modern marvel. But so far it means you have to buy their telescope first . Then move its phone cradle to your telescope.

SkEye app works pretty good as well for push-to usage.  You'll just need to rig up a phone holder starting with a car phone clamp to attach it to your scope.

[AlexK]

22 hours ago, Louis D said:

SkEye app works pretty good as well for push-to usage.  You'll just need to rig up a phone holder starting with a car phone clamp to attach it to your scope.

The SkEye is the best app so far at utilizing smartphone's accelerometers/gyro sensors indeed. But it is still a "poor blind thing". So if the phone mishaps you may end up pointing into an opposite direction  The CSSE tech is actually "seeing" where the telescope is pointed between stars (leveraging the "plate solving" algorithm). That's an ultimate advantage over everything else for amateur-grade telescopes pointing known to men to date except for their very own eyes

On a side note, there are plenty of star charting apps leveraging the same sensors array as the SkEye to help matching the view in the sky with the chart on the screen, just bring the phone up above your head (with the feature ON). You can easily use that for the rough telescope pointing too without any cradle needed, here is how step by step: 

1. Zoom the chart to have some natural field of view chart displayed, e.g. 20 deg FOV screen width.
2. Mark your desired target on the chart so it's easy to track on the screen.
3. Place the phone screen against the rim of your UTA (don't worry, most screens are scratch resistant enough) so it is orthogonal to the optical axis (most UTA rims are, just make sure phone is not rocking on it) and so that you can see the center of the screen (some apps have the center marker or the EP FOV overlay feature, so just turn that ON for your widest eyepiece.
4. Now just move the OTA (right by the rim where you are holding the phone, no need to look through the EP or a finder) until your target is centered on the chart.

Done! 

Depending on your phone sensors accuracy (and less so on your optical axis orthogonality and collimation), you may end up right on the target with your widest EP. That's exactly how I've been finding the recent NEOWISE comet in the small clearing in the trees before the civil dusk was over (barely single star visible that low West) for example, as when I can see stars around my invisible target the QuInsight helps to point even better than the CSSE, and surely much faster, as it's leveraging my eyes and brain not some dumb microcomputer .

Edited January 15, 2021 by AlexK

[Spile]

Prompted by this thread, I got the urge to attach my phone to the OTA using the finder scope (I can still see through it) eyepiece barrel  to see if SkEye will perform as an alternative finder.

I plan to use this guide - https://lavadip.com/media/SkEyeIntro.pdf

 

 

[wibblefish]

Interesting tech solutions there be good to know how it goes @Spile Ill still be waving my phone around my head with skyview in the meantime 🙈

[AlexK]

1 hour ago, wibblefish said:

Interesting tech solutions there be good to know how it goes @Spile Ill still be waving my phone around my head with skyview in the meantime 🙈

That's exactly the same tech, just SkEye taking it more seriously. For example, you don't have to wave the phone high above with the screen down after calibrating the SkEye by pointing at a bright star just once, so it will be more convenient to use when mounted on the telescope right by the EP (main or findre's). But you can try my method above with your SkyView app already (as I understand, you've got the iPhone, which is not supported by SkEye).

On a side note, for those stuck with an iPhone, I could recommend getting a secondhand Android "phablet" for dedicated astronomy use (should be well under a $100 price tag of a cheap eyepiece nowadays). That way you are not only expanding your handheld computing capabilities, but also reducing the chance damaging your actual phone and losing the connection to the world. Which might be even life threatening in some rural dark sky "expedition".

[wibblefish]

Sorry to dredge an older thread but wanted to provide an update!

Finally got first light with my 6x30 RACI and its changed my life. I am eagerly awaiting the Rigel to get RDF back but wow to finderscopes. Can actually see stars to hop and target when in the wash out from the moon etc. 
 

I did have a small issue with the EP steaming up but it cleared quickly.

One minor niggle is that whilst its correctly set for my 25mm when changing EP it is no longer centered but I guess thats to be expected as its a fixed focal point 🤔

Edited January 31, 2021 by wibblefish

[Zermelo]

2 hours ago, wibblefish said:

Sorry to dredge an older thread but wanted to provide an update!

Finally got first light with my 6x30 RACI and its changed my life. I am eagerly awaiting the Rigel to get RDF back but wow to finderscopes. Can actually see stars to hop and target when in the wash out from the moon etc. 
 

I did have a small issue with the EP steaming up but it cleared quickly.

One minor niggle is that whilst its correctly set for my 25mm when changing EP it is no longer centered but I guess thats to be expected as its a fixed focal point 🤔

Good to hear it.  I'm equally impressed with mine, in the short time I've had it.

Was it the eyepiece that steamed up or the objective lens? I did have dewing issues with the objective but found a scrap piece of plastic tube the right size that I push on when I need to.

The alignment shouldn't change with different eyepieces, more likely that it's difficult to judge the centre of an EP field without crosshairs. I line up the scope on a point with a wide EP, then switch to the shortest I have, centre that as best I can and then adjust the finder onto the same point. I do it daylight on a terrestrial target so that it's not moving. By using a shorter EP the field is narrower, so any error in judgement will be smaller in real terms.

[wibblefish]

1 hour ago, Zermelo said:

Good to hear it.  I'm equally impressed with mine, in the short time I've had it.

Was it the eyepiece that steamed up or the objective lens? I did have dewing issues with the objective but found a scrap piece of plastic tube the right size that I push on when I need to.

The alignment shouldn't change with different eyepieces, more likely that it's difficult to judge the centre of an EP field without crosshairs. I line up the scope on a point with a wide EP, then switch to the shortest I have, centre that as best I can and then adjust the finder onto the same point. I do it daylight on a terrestrial target so that it's not moving. By using a shorter EP the field is narrower, so any error in judgement will be smaller in real terms.

Ah I will try that thanks I didnt think about using the shorter EP that for some reason!

The finder eye peice rather than the objective but left it alone a few mins and it seemed to be fine!

Mine didnt come with any instructions on how to sort it though I have managed the only bit Im unclear on is the metal bolt that sounds like it has a spring near the eye peice. I guessed it was to hold the scope inside the rings with different tensions then allow you to make better fine adjustments (as one of my small screws is basically all the way out) but it didnt actually change anything that I could ascertain.

 

[Zermelo]

3 minutes ago, wibblefish said:

the metal bolt that sounds like it has a spring near the eye peice. I guessed it was to hold the scope inside the rings with different tensions then allow you to make better fine adjustments

Yes, some finder holders have three screws at 120 degrees, but that one has two screws and a spring-loaded pin. You leave the pin alone, and adjusting the two screws allows you to orient the tube in the plane just as well as three screws would (and is probably easier).

[Pixies]

A quick pic and we'll be able to tell.

I also find the eyepieces of RACI finders are easy to breathe on, if you're not careful. That soon steams them up.

[wibblefish]

Makes sense then Ill have to do what you suggest @Zermelo

@Pixies sure here is a low res one lol! Yeah I imagine thats what happened I usually try to not breathe when first looking lol

 

[Pixies]

Yep. The silver bolt is sprung loaded and acts as a pivot. You adjust the 2 screws to align the finder in the 2 perpendicular axes.

[Tiny Clanger]

8 hours ago, wibblefish said:

Sorry to dredge an older thread but wanted to provide an update!

Finally got first light with my 6x30 RACI and its changed my life. I am eagerly awaiting the Rigel to get RDF back but wow to finderscopes. Can actually see stars to hop and target when in the wash out from the moon etc. 
 

I did have a small issue with the EP steaming up but it cleared quickly.

One minor niggle is that whilst its correctly set for my 25mm when changing EP it is no longer centered but I guess thats to be expected as its a fixed focal point 🤔

Good, aren't they ? Make finding the dim stuff much easier. I was skeptical about if it was worth spending the money on one, but it really is. You just need to go through the same rigmarole to line it up accurately as you did with the original RDF  (and will do again with the Rigel !) but it's not much of a problem, I have to tweak mine when it goes from one 'scope to the other and find it pretty quick to do.

I've caught myself admiring  a star cluster in the RACI  for a few minutes and had to remind myself it's not the actual telescope ...

4 hours ago, Zermelo said:

Yes, some finder holders have three screws at 120 degrees, but that one has two screws and a spring-loaded pin. You leave the pin alone, and adjusting the two screws allows you to orient the tube in the plane just as well as three screws would (and is probably easier).

 

Or in my case, .to attempt to improve the accuracy of the raci targeting by twiddling the sprung pin, mistaking it for one of the screws in the dark. 🤡

I was slightly surprised by the lack of instructions too, especially as my urge for orderliness was vaguely disturbed by the sighting cross not being (as far as I can see) able to be rotated . It doesn't bother me now, and I suppose it shouldn't ever have, the centre is the centre , but still ...

I made mine a teeny little dew shield of its own for the front element,  from a scrap of the foam I bought to make the dob shroud/dew shield from : no idea if it does any good, but it stays on permanently and certainly does no harm . The RACI has not dewed up at either end .    Yet. Neither has the Rigel, which surprised me.

Heather

[AlexK]

Congrats.
I have eventually removed my optical finder and using the Orion 7220 in ACI (not RACI, as the angle is not straight ) mode in the finder shoe. Not for finding objects but simply for binoculars-like views (surely I can point with it too just replacing the wide EP with the reticle equipped one or simply centering a bright target). That ACI is great for standalone viewing too:

[John]

I now find that RACI optical finders do practically all I need in terms of finding with my refractors. I do use the Rigel Quikfinder and 9x50 RACI optical combo on my 12 inch dobsonian. The 100mm and 102mm refractors have their own 6x30 RACI's and the 120mm and 130mm refractors, 9x50 RACI units. I have a couple of spare Vixen RDF's knocking around just in case I feel that's a better tool for a particular task but 90% of the time the RACI opticals get the results.

The slight downside is that I now have a collection of 5 RACI's and 3 illuminated reticule finders.

While the Skywatcher type finder mounts with the sprung pin and two nylon screws do work pretty well, I have a couple of finder mounts that use three screws at both ends and those hold finders much more solidly, virtually never needing re-adjustment with the main scope optics. This type of finder mount:

I like my finders to be aligned to the point that what is on the centre of the cross hair will be in the centre of the field of view at 200x plus though the main scope.

Edited January 31, 2021 by John