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Discovery 150i & eyepieces on order - what else do I need?


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Hello all

I have a Sky-Watcher Star Discovery 150i WiFi https://www.firstlightoptics.com/az-goto/sky-watcher-star-discovery-150i.html on order from FLO, which I hope to get in the next week or so (fingers crossed). I have also ordered a 2x Barlow and a BST StarGuider 18mm eyepiece, a Baader Hyperion 24mm and a Baader Hyperion 8mm.

I was wondering what else I need to get to hit the ground running? I'm interested in observation only (both planets and DSOs if possible), and live in north west London.

My thoughts at the moment are a BST StarGuider 5mm eyepiece and a Celestron Lithium Powertank https://www.firstlightoptics.com/batteries-powerpacks/celestron-6-1-ah-powertank-lithium-lt.html

Anything else I should get? Any recommended filters to cope with light pollution? Dew hood?

Thanks for your advice.

Old Clive

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Hi , i don't think you need to worry about a dew shield ... as for filters , i would try the scope without them first . It's a really nice scope and a good size too , plus the mount is a nice solid platform . a powertank is a good idea . It's tempting to buy everything and anything ( been there done that ) . 

Stu 

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Get a good guide to start with. Turn left at Orion is often recommended, but there are others, such as Nightwatch: https://www.abebooks.co.uk/Nightwatch-Dickinson-Terence-Firefly-Books/30442906126/bd?cm_mmc=ggl-_-UK_Shopp_Tradestandard-_-product_id=COUK9781554071470NEW-_-keyword=&gclid=Cj0KCQjwsqmEBhDiARIsANV8H3ZVC0VNWFhVuzJBp5-_vcvLCtAZYr20VIfwiRDwv5QkEYEAmgE_PVAaAhCWEALw_wcB

You don't have to rush in to quickly. Get used to what you have, then you can see where you might want to make improvements. It's easy to end up with loads of stuff you don't use!

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I'm a little under a year ahead of you with the 150i.

With the eyepieces you have already ordered (including barlow combinations), you will get 31x, 42x, 63x, 83x, 94x and 188x (leaving aside the 10mm and 25mm EPs that came with the scope). You have a gap between 94 and 188 that you might want to fill, for planets and double stars. The 5mm would give you 150x and 300x barlowed. I bought a BST 5mm recently and I thought it performed better than a similar power obtained with the barlow. As you may know, 300x is about the theoretical maximum for the 150i when seeing is very good. Since I've had my scope, there has been one night when I've used 300x very successfully, and two or three others when it wasn't so good, but didn't blow up. The rest of the time the limit was between 150x to 200x. Zooms can be very handy, but you may want to hold off on that as you have a few fixed EPs.

A power supply (other than AA batteries) is a must. I made my own from a lead-acid battery. You will find several threads elsewhere discussing various choices from car starters to leisure batteries. The one you mention isn't the cheapest option, but it looks well-designed and will be light. 6Ah should be fine for a session unless you try to run a lot of other stuff from it. 3A peak load is more than enough for the Star Discovery mount. Did you check that the Celestron cable will also fit the SW mount?

The scope doesn't suffer much from dew. I did make my own guard for the top end (to protect the secondary) but I'm not sure how much of a difference it's making. On rare nights when it's been very bad, my eyepieces and finder are misting up first, and when my books start to get damp I call it a night.

Turn Left has already been mentioned, and has proved very useful. I use Stellarium on a laptop when planning, and SkySafari Plus on my phone for planning, controlling the scope and recording observations. I have found that the tech has really contributed a lot to the experience, but I know that's very subjective. I made a physical red filter for my phone, as I found night modes unreliable.

I dispensed with the red dot finder and stuck a Telrad on the back end of the OTA. I used the vacant finder shoe for a 6x30 RACI, and I find the combination of Telrad+RACI+SkySafari to be very effective. Combined with a heavier EP, I'm pushing at the limit for the mount, but it doesn't seem to be a problem.

As others have said, filters can probably wait a bit. Planetary filters won't be needed urgently. You can think about a UHC or OIII for emission nebulae, though you're looking at close to three figures for a good one. It helps a lot on the right object (e.g. the veil) but in most cases I've found the views with and without a filter are both worthwhile, though different. Possibly six inches isn't enough aperture to make the most of them. Sky pollution filters I've avoided, being persuaded that ubiquitous LED lighting has reduced their effectiveness. I believe IDAS types give some success, but they are not cheap. The only filter I would get straight away is a moon filter. I got a 25% ND type, which is a reasonable compromise for a 6" scope, but sometimes you want more and sometimes less. With hindsight I'd go for a variable polarizing type, they're not expensive.

Clothes - be ready for next winter. You can never have too many layers. I eventually found a combination that did the job, but after many iterations. Hands are the worst - have a read about what people have tried with gloves. I've never managed to operate successfully with both hands gloved, so pocket handwarmers are worth considering.

Think about any annoying neighbour lights that are going to impinge on your viewing area, and whether you need to set up screening. I don't bother on moonlit nights, but on the darkest ones it can ruin your night vision.

I suspect you have lighter skies than me (if you'll be observing from home), so finding objects will be more challenging. The goto can be a real help (especially used with a RACI) but it has some quirks and it has taken me a while to get the most out of it - I suspect it's down to me settling into a regular mode of operation and refining the setup.

You should get a lot out of the 150i.  At F/5 it will give you decent views of larger DSOs (up to about 2 degrees TFOV) but you can still push it a bit the other way for doubles when the conditions allow (I've managed down to 2.2" so far). You won't see much of planets at the moment of course, it will be a while until Jupiter and Saturn are better placed, but I did get some good views of Mars last year when it was close.

 

 

 

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On 04/05/2021 at 16:52, Zermelo said:

 

I dispensed with the red dot finder and stuck a Telrad on the back end of the OTA. I used the vacant finder shoe for a 6x30 RACI, and I find the combination of Telrad+RACI+SkySafari to be very effective. Combined with a heavier EP, I'm pushing at the limit for the mount, but it doesn't seem to be a problem.

 

Hi Zermelo and thanks for all the guidance & info 👍

I was wondering why you would need both a Zelrad and a 6x30 RACI? Aren't they both finders that essentially do the same thing?

And if you were to just have one, which would it be?

Thanks

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Posted (edited)
17 minutes ago, Old Clive said:

I was wondering why you would need both a Zelrad and a 6x30 RACI? Aren't they both finders that essentially do the same thing?

I see a Telrad as a version of a Red Dot finder (RDF) they seem to work in a similar way, but a Telrad obviously has the red circles on it which many people find useful.  I don't own a Telrad, but I do have a standard RDF and a RACI optical finder on my own telescope.  As with @Zermelo I find the combination of both finders incredibly useful.  I use the RDF which gives a clear view of the sky around the finder as well as through it to get the telescope roughly in the right place - I find that you can even use the RDF in this way for rough finding even without it being adjusted spot on, then what I find is that if the RACI optical finder IS Spot on that if you are roughly in the right bit of sky through the RDF then what I am seeking is usually visible in the optical finder and then it is a simple matter to get the optical finder spot on when it is incredibly difficult to do so just looking through the RACI as it is magnified and also you can only see the bit of the sky visible through the optical finder without a lot of faffing about and both eyes in use.  Yes, you could just use a spot on Telrad or RDF alone, but the magnification of the optical RACI is useful for getting stars nicely central in the telescope once you know the optical RACI is spot on centralised and obviously the optical view is handy for stars that are just out of eye sight once you know the RDF has put you in the rough area the RACI can then stand a better chance of finding the star you are after and you KNOW that its pointing in the right area.  I went from finding very little within 1/2 hr with just the RACI to finding stuff within 5 minutes with my RDF, but with both working I can hit anything I can see with my eye in <30 seconds.  IMO there is absolutely value in mounting both types of finder.  I have a computer driven scope, but I still need to find stars for calibrating it each time and wasn't up and running quickly until I had both finders mounted.

Edited by JOC
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7 minutes ago, JOC said:

I see a Telrad as a version of a Red Dot finder (RDF) they seem to work in a similar way, but a Telrad obviously has the red circles on it which many people find useful.  I don't own a Telrad, but I do have a standard RDF and a RACI optical finder on my own telescope.  As with @Zermelo I find the combination of both finders incredibly useful.  I use the RDF which gives a clear view of the sky around the finder as well as through it to get the telescope roughly in the right place - I find that you can even use the RDF in this way for rough finding even without it being adjusted spot on, then what I find is that if the RACI optical finder IS Spot on that if you are roughly in the right bit of sky through the RDF then what I am seeking is usually visible in the optical finder and then it is a simple matter to get the optical finder spot on when it is incredibly difficult to do so just looking through the RACI as it is magnified and also you can only see the bit of the sky visible through the optical finder without a lot of faffing about and both eyes in use.  Yes, you could just use a spot on Telrad or RDF alone, but the magnification of the optical RACI is useful for getting stars nicely central in the telescope once you know the optical RACI is spot on centralised and obviously the optical view is handy for stars that are just out of eye sight once you know the RDF has put you in the rough area the RACI can then stand a better chance of finding the star you are after and you KNOW that its pointing in the right area.  I went from finding very little within 1/2 hr with just the RACI to finding stuff within 5 minutes with my RDF, but with both working I can hit anything I can see with my eye in <30 seconds.  IMO there is absolutely value in mounting both types of finder.  I have a computer driven scope, but I still need to find stars for calibrating it each time and wasn't up and running quickly until I had both finders mounted.

Thanks for the reply JOC, much appreciated and very useful.

But as my scope is (or will be when it arrives!) is a 150i, with the wi-fi GoTo mount, don't I just need one finder to get the initial line-up correct then the scope will go to whatever I want to look at?

Sorry if I'm asking silly questions....🥺 When I get my hands on the scope and start using it all this might start making sense!

Thanks

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Some great advice above, my advice would be to get an app for your phone and get out into the area that you are going to observe from and understand how the app works. Find Polaris, then make sure that the app aligns with both North and Polaris (ish) and then just look around and start to identify some of the brighter stars out there. I have to mention a planisphere as I use one, I find it easy to use to identify the brighter stars quickly. HTH

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25 minutes ago, Old Clive said:

Thanks for the reply JOC, much appreciated and very useful.

But as my scope is (or will be when it arrives!) is a 150i, with the wi-fi GoTo mount, don't I just need one finder to get the initial line-up correct then the scope will go to whatever I want to look at?

Sorry if I'm asking silly questions....🥺 When I get my hands on the scope and start using it all this might start making sense!

Thanks

I agree with @JOC, I could probably work in the same way with a simple RDF+RACI. I don't really use the outer Telrad rings, I use the centre to start off and then use the RACI for fine tuning/hopping. To be honest I was experimenting for a while and didn't really know what would work for me until I had my current setup. One reason for switching to a Telrad was that it freed up the finder shoe, and I wanted to use it for a magnifying finder. But I could have bought one of these instead and mounted a RACI alongside the red dot, and perhaps not bother with the Telrad.

Also, I would manage your expectations just a bit with the power of computerized goto. I like it and use it a lot, but it isn't perfect.  The claim is that it should put your target within the field of a low power eyepiece, and most of the time it does just that. But I have found that it can have "good days" and "bad days". I was out last week and it was excellent, steering me to a globular cluster almost spot on at 150x. But I have also had sessions when the targets are outside my widest-field eyepiece, and that's when a magnifying finder (covering about 7 degrees of sky) is useful. You can see fainter stars than you would with the naked eye, and matching the pattern with a star chart or (in my case) an app allows you to navigate to the correct place. And even if the Goto does put a target within the eyepiece FOV, it may not be obvious which it is, e.g. a very tight double star in a busy starfield, or a compact planetary nebula. But if you have matched the star patterns, you can identify the target in the finder using your star chart. Even if the target is too dim to show in the finder (a faint galaxy, perhaps), you can use the cross hairs to point the scope at exactly the right place, and it should appear in the eyepiece. This has worked so well that I find I can often leave a high-power eyepiece in situ and not need an intermediate step with a longer EP. I originally tried all this with an inverting straight-through finder (cheaper, more available), and couldn't get the hang of reversing everything, hence the RACI. Others can do this without problems. And if your're using an app like SkySafari or Stellarium, it can reverse the charts to match a straight-through view.

And no, none of these are silly questions. The advice on this forum is excellent, but there are some things you just need to try out for yourself and see how you get on. Try working with the red dot for a while, try the goto, and take it from there.

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2 hours ago, Old Clive said:

But as my scope is (or will be when it arrives!) is a 150i, with the wi-fi GoTo mount, don't I just need one finder to get the initial line-up correct then the scope will go to whatever I want to look at?

Yup, mine also has a WiFi goto mount - yours might be slightly more clever than mine, but I need to select stars in the sky and be able to tell if the telescope is looking precisely at them to confirm the calibration is correct so that I can inform the computer (this will change whenever you go out unless you have a permanent mount).  Don't underestimate the difficulty of finding the stars in the sky through a telescope optical finder or just through the telescope until you've tried it.  The thing is some telescopes can be unbalanced really easily (at least mine can 8" 200P Dobsonian) by the claptrap attached to them like heavy Eye pieces, dew shields, dew bands - and I guess heavy finder assemblies!!  Thus when you start off the calibration with the telescope pointing north (I find Polaris manually - using the finders!! and then make the scope horizontal) and you tell the scope to find i.e. Capella as a novice the scope appears to drive to the star and asks you to centre the star and confirm on the computer.  You excitedly peer into the EP and.......duh...........where on earth is that star - just because the system thinks it's got it right, it might not (on my scope it is often because I've got a big EP in the system - mine works best just with the setup and EP's it was supplied with for calibration - and a bit/lot of manual tweaking of the position might be in order - that's where your finders come in - you find the star with them and then confirm to the system and try the next one (you need two or three stars to callibrate).  In use once calibration is done I often find that it will drive OK to the correct 360 horizontal location, but if I've got lots on board it sometimes won't drive vertically - not a huge problem with finders on board, you can push mine without upsetting it and just tip it up until I have the star in the finders - again another use for finders.  

The Goto's are good once they are up and running and calibrated, I've found stuff with the Goto's that I would never have seen without them by star-hopping, but as above they are ABSOLUTELY NOT infallible and having finders is also handy when all you want is a quick peak at Jupiter which is easy to find by eye with quick look at an appropriate finding app on the phone and just want a quick setup without setting up the electronics - assuming your scope lets you push to targets which mine is quite happy to do.  

All of the above is based on real experience.  I'm still a real beginner like yourself, and my hiccups and solutions might prove useful?

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