A n00b with a £250 limit

[Karo]

The 25mm EP that comes with the scope isn't bad, the 10mm aint so great. Both are adequate to get started, though virtually anything >£30 would be an improvement. I use a Skywatcher Extraflat 19mm with mine, for the money (about £42 IIRC) I've been quite impressed so far. To start with you wont need anything else but a moon filter or neutral-density so that the moon is not uber bright -- optional though, you just wont be able to see much for a while after looking at the unfiltered moon.

[Astro_Baby]

Moon filter is good, the supplied EPs and Barlow arent as bad as some people suggest. I found the 25mm and the Barlow pretty good myself - certainly good enough to get started with.

Get some eyetime in before buying more stuf would be my advice and keep a look out for decent 2nd hand bargains on eyepieces.

[hoobz]

I'VE MISSED THE POSTY!! NNNOOOOOOOOOOOOOOOOOOOOOO !

lol, pickin it up at 6. whoo hoo.

[hoobz]

she's here, she's beautiful! the moon looks like well erm like i didn't think it would lol, cant seem to get to motors workin at mo. gonna be a long night. its clear as hell here. the moon's a bit bright tho i guess!?

[Vulpecula]

First accessory you will need is a red light torch and a power tank to power it from.

Disagree with the power tank.

Those things are over-specified, bulky, and (for SkyWatcher/Celestron ones) considerably over-priced.

All you need is a handful of rechargeable batteries.

Much lighter and far more portable.

[steve_bham]

Disagree with the power tank.

Those things are over-specified, bulky, and (for SkyWatcher/Celestron ones) considerably over-priced.

All you need is a handful of rechargeable batteries.

Much lighter and far more portable.

I agree with astro-baby. Powertanks are a must for long observing sessions. A handfull of batteries are ok if you just want a quick session. But if you look around you can get good offers. Just about to buy a 40AH powerpack for £40.

I also have the 7ah Celestron one which powers scope all night.

[Vulpecula]

Powertanks are a must for long observing sessions.

Bit of a blanket statement there Steve :-)

It clearly depends on the power-draw of your scope.

AA batteries won't power an observatory-class tracking mount all night long, but the common SkyWatcher SupaTrack mount can last several long evenings on a single set of AA batteries.

[steve_bham]

Bit of a blanket statement there Steve :-)

It clearly depends on the power-draw of your scope.

AA batteries won't power an observatory-class tracking mount all night long, but the common SkyWatcher SupaTrack mount can last several long evenings on a single set of AA batteries.

Disagree slighty, as they just dont have the power output to keep stable tracking. But hey each to their own.

[Vulpecula]

they just dont have the power output to keep stable tracking.

The SupaTrak mount is centered around a pair of 8-Bit CMOS flash microcontrollers which drive individual stepping motors on each axis. As a digitally-controlled system, fluctuating battery power levels have no effect on tracking accuracy or stability until the batteries start to lose the ability move the motors - which, as I say - takes several evenings' observing.

Other mounts are - I'm sure - more demanding.

[steve_bham]

The SupaTrak mount is centered around a pair of 8-Bit CMOS flash microcontrollers which drive individual stepping motors on each axis. As a digitally-controlled system, fluctuating battery power levels have no effect on tracking accuracy or stability until the batteries start to lose the ability move the motors - which, as I say - takes several evenings' observing.

Other mounts are - I'm sure - more demanding.

Say the motors are rated at 750mA 12v. Rechargable batteries rated at 1.25v 1500mA

8 batteries = 10v 1500mA. Without factoring the voltage drop or the battery degradation (if you want the formula let me know and imm pm it you) you would at best get 2 hours viewing time.

Cost of 8 GOOD batteries just short of 15 quid.

7AH power pack gives you at best just over 9 hours.

Cost of a cheap 7AH 30ish quid.

I know its a simplistic view as you need to take into account current drawn voltage drops, temp, degradtion etc etc. but my point being long term battery packs are a good investment and in MY eyes a must have.

[arad85]

Steve, you are correct for a Goto SCT but that is controlling a LOT more than stepper motors that are just set to track sidereally (only one will be going when tracking). The SCT you have has a micro in it doing all the calculations to track in both alt and az at the same time. I'd expect the motors in the dual axis drive to take a lot less than 750mA when tracking and there is no computer to power either. If they didn't work for a reasonable amount of time off a battery pack, they would be sold with a 12V cigarette lead as well..

[arad85]

PS: those drives run on 4xD cells, so are only 6V, not 12V. A D is "normally" 2200mAh so skewing the calculations a bit

[steve_bham]

Oh sorry! thought it had stepper motors in etc. But you still only get nominal voltage of 1.2v, if using a rechargable battery.

You can get "speciality batteries" that under load will work at 1.5-1.6v, but you pay the price.

[Vulpecula]

My AA batteries are 2500mAh (£12.99 for 8)

You can also get 2700mAh ones.

[Vulpecula]

Say the motors are rated at 750mA 12v.

Steve, here are actual figures (measurements just taken) for a Sky-Watcher SupaTrak Alt-Az tracking mount:

• Power on = 52mA
  
• Slew on either axis = 85mA to 140mA (depending on speed)
  
• Slew on both axis at once = 230mA (max)
  

- and the one we're most interested in:

• Auto tracking = 128mA
  

This explains why a set of AA batteries will last several evenings with a Sky-Watcher SupaTrak mount.

[steve_bham]

Steve, here are actual figures (measurements just taken) for a Sky-Watcher SupaTrak Alt-Az tracking mount:

• Power on = 52mA
  
• Slew on either axis = 85mA to 140mA (depending on speed)
  
• Slew on both axis at once = 230mA (max)
  

- and the one we're most interested in:

• Auto tracking = 128mA
  

This explains why a set of AA batteries will last several evenings with a Sky-Watcher SupaTrak mount.

Dont forget to factor in temp, battery memory status, degradation, how many times slewing etc.

But like i said each to there own

[Astro_Baby]

Okies - I'll step in and say my original HEQ5 was powered by 8x 1.5v C cells. Total cost for rechargeables about £35 - cos of a charger to charge them £10. So £45.

OR I could buy a 17aH power tank for £40 - easy choice I think.

How long do rechargable NiCads and NiMHS last ? Forget the manufacturer hype - the answers not so long when the going gets tough. I used to be a pro photographer and rechargeable 2600MaH batteries never lasted long either in camera run time or life cycle. Most were destroyed very quickly by constant recharging. Manufacturers always claim "Over 20 zillion recharges blah blah blah" in reality mine never lasted at the very most more than a hundred recharges and frequently far less.

My EQ2 used a batch of AA batteries and I used to use rechargeable AAs from my cameras. It lasted ok - sort of. Do you want the one clear night this month messed up by a scope whose mount is supplied by a 'sort of' approach to power. When your out there freezing on a hillside in the dead of night the last thing you need is extra hassle with equipment. Cold, especialy extreme cold at night when its damp in the winter months, just kills batteries.

Also, at the end of the day, you are going to upgrade in this hobby - probably faster than you may believe. So a bigger power tank makes sense for that. It also makes sense economically.

Would you rather pay £40 for some recharagbles and a charger or £40 for a 17aH battery pack (which also has a torch) and will drive almost any scope for a minimum of 4 hours even the gutsy and power hungry HEQ5 of mine and dont forget when the dew starts on your scope you may just need a 12v hairdryer - you'll be very grateful for a bigger power supply when the moment comes as a lot of reflector owners will testify to. Hairdryers and dew strips suck power super bad.

Thats my take - I could do the math as well about consumption, wattages, amperage, cold effects BUT experience tells me get as much power as you can - you'll never be sorry you have too much and at £40 for 17aH its happiness on the cheap.

[Vulpecula]

Do you want the one clear night this month messed up by a scope whose mount is supplied by a 'sort of' approach to power.

I consider it normal to carry spares.

I could do the math as well about consumption, wattages, amperage, cold effects.

I didn't imply otherwise.

[Astro_Baby]

That wasnt a pop at you honey - I didnt intend it to sound combatative in anyway - yes I know you could take spares but my take is that once your in a field the less hassle the better. Most scopes will end up needing anti-dew to a greater or lesser degree. A power tank will guarantee that the powers available for anti-dew measures and anything else you may need to power.

I dont disagree that the Celestron/Sky-Watcher ones are overpriced - I have a 7aH Celestron one thats very handy as it has a huge torch on it but the scopes pwered off a Maplin powertank which was pretty reasonable at £40. In fact if you take a shop second off them they will bash it out for £20.

My own experiences with small recharable batteries is very far from positive hence my advice to get a power tank - obviously we differ on this - thats cool.

Another accesory that should be considered as a bit of a priority though is a dewshield. The past two years at Salisbury have seen people stuffed up by the scope dewing badly.

[Vulpecula]

I dont disagree that the Celestron/Sky-Watcher ones are overpriced

It's a shame, since I actually like the concept of the big SkyWatcher one with the built-in radio. I could afford it - but there's a limit to how much I'll allow my enthusiasm to be taken advantage of. Ironically the final turn-off was that the "cranking-amps maximum" was under-specified for my needs (I have one of these modern cars where apparently it is "normal" for the battery to go flat if the car is unused for a month; it needs powerful cranking.)

In the end I did get a low-cost Argos one (for when the car's been left unused), but it's still in the box and I've not felt the need to use it for astronomy.

Another accessory that should be considered as a bit of a priority though is a dewshield.

- plus of course Hoobz will also need to buy a Cheshire Collimator tool for that scope.