allcart

I checked the heavens above site tonight to see what time it is due. On the data table it showed that the ISS would have a brightness mag of -3.4 at 10.22pm. At midnight it will be -0.6.

What does this mean exacly?

See! all your years of learning wasn't wasted after all. Its just that my learning was on a different curve.

Thanks Richard, I may get to understand this stuff yet.

Thanks Danielle, very helpful.

so if I understand this, the 620 ohm strap will produce less heat due to the higher resistance and lower wattage, but will not drain the battery as quickly.

The 330 ohm strap produces more heat due to lower resistance for the same number of resistors in the chain, and produces more wattage etc, but will drain the battery quicker.

My goal is to make a dewstrap that produces slightly more heat than I need, but can be regulated with a dew controller.

just not sure how much heat I actually need yet.

I'll start by saying that I don't understand electrical theory, so I need to pick your brains.

Ok, so I have made a couple of dewstraps to run of a 12V 7AH battery.

One strap has 10 x 620 ohm 1/2 watt resistors in parallel.

other has 10 x 330 ohm 1/2 watt resistors in parallel.

Q. which will provide more heat? and what will be the wattage of each strap?

Q. If I add a resistor, does it increase the wattage and heat, or reduce it?

I appologise for my lack of understanding, but some things we know and some things we don't.

allan

Thanks Stu, I was typing at the same time you were so didn't catch your post. I'll bookmark that link too.

Its ok, I searched and found what I needed. It seems from what I read that it is getting lower now, so may be not as bright close at it eas last night. Shame it was cloudy here.. I'll be watching the shies over the next couple of days though.

I saw the ISS lastt Saturday night. Definately a wow moment. Does any have the link to the ISS website so I can find out when it will be around again.

Thanks all, I sold my scope a while back so I will have to stick with the dslr and lenses. One really expensive hobby is enough. I can photograph at over 1000mm with my lenses, so that should be good for a bit of tele viewing.

i bought some from maplins but these are rated at 6 amp dear though £7 each lol

Could you provide a link to the maplin item please.

Allan

Hi everyone. i am obviously new here but want to introduce myself. I live in Hampshire, UK. I work too much, and have a photography business as well, so have little time for the fun stuff I enjoy. I dabbled with astronomy several years ago, but found that the best time for stargazing is when I should be asleep, so I stopped it. Now I find my interest is awakening again and instead of telescopes, I can use my cameras. Life is getting sweeter.

Allan

Hi Folks, I have been searching for something like this since the weekend.

I'm a photographer with an interest in astrophotography, but never really have the time to do it. Well, up until last weekend when I joined my local astronomical society to watch the Perseid meteors. I was taking pics with my dslr but suffered fron dew buildup on the lens. After a quick bit of research I found plans for dew straps and made a couple. I realised after making them that I have no way of controlling the temp.

Is this dimmer control all I need to adjust the temp?

Thanks

Allan.